ORIGINAL RESEARCH

published: 09 May 2019

doi: 10.3389/fpsyt.2019.00284

Use of the Pittsburgh Sleep Quality

Index in People With Schizophrenia
Spectrum Disorders: A Mixed
Methods Study
Sophie Faulkner 1,2* and Chris Sidey-Gibbons 3,4
1School of Health Sciences, University of Manchester, Manchester, United Kingdom, 2 Greater Manchester Mental Health
NHS Foundation Trust, Manchester, United Kingdom, 3 Patient Reported Outcomes, Value & Experience Center (PROVE),
Brigham and Women’s Hospital, Boston, MA, United States, 4 Faculty of Surgery, Harvard Medical School, Boston, MA,
United States

The Pittsburgh Sleep Quality Index (PSQI) is a measure of self-reported sleep quality and
sleep disturbance. Though the PSQI is widely used, it is unclear if it adequately assesses
self-reported sleep disturbance in people with schizophrenia spectrum disorders. We
used mixed methods to examine the relationship between scores on the PSQI and
qualitative self-report during in-depth interview in a group of participants diagnosed with
Edited by: schizophrenia spectrum disorders (N = 15). Although the PSQI appears to accurately
Joseph Firth, capture issues related to sleep initiation, average duration, and interruption by physical
Western Sydney University,
Australia
complaints, it did not adequately assess other salient issues including irregularity in sleep
Reviewed by:
duration and timing, shallow unrefreshing sleep, prolonged sleep inertia, hypersomnia,
Sérgio Arthuro Mota-Rolim, and sleep interrupted by mental or psychological complaints. In interview by contrast
Federal University of Rio Grande do these types of problems were readily reported and described as important by participants.
Norte, Brazil
Aliyah Rehman, Our findings suggest that using the PSQI summary score as a measurement of general
University of Glasgow, sleep disturbance in this population may be misleading, as this failed to capture some of
United Kingdom
the types of sleep problems that are particularly common in this group.
*Correspondence:
Sophie Faulkner Keywords: screening, outcome measure, psychometric, interview, qualitative, psychosis, circadian rhythm
sophie.faulkner@manchester.ac.uk disorder, insomnia

Specialty section:
This article was submitted to INTRODUCTION
Schizophrenia,
a section of the journal The Pittsburgh Sleep Quality Index (PSQI) is a widely used self-reported questionnaire measure of
Frontiers in Psychiatry sleep (1). The PSQI is practical and brief, returning a single score representing overall sleep quality,
Received: 27 August 2018 which incorporates qualitative and quantitative aspects of sleep; scores above 5 are suggested as
Accepted: 11 April 2019 indicative of a potential sleep problem. The PSQI includes open-ended questions that can be used
Published: 09 May 2019 to identify the nature and possible causes of sleep problems to help direct treatment (2), and gives
Citation: subscale scores that can indicate the type of sleep problems (sleep duration, latency, disturbances,
Faulkner S and Sidey-Gibbons C quality, efficiency, daytime dysfunction, and use of sleep medication), as well as some questions on
(2019) Use of the Pittsburgh Sleep
indicators of sleep apnea.
Quality Index in People
With Schizophrenia Spectrum
The PSQI was initially developed with a sample of people with depression, healthy sleepers,
Disorders: A Mixed Methods Study. and people with sleep disorders (2). Many authors, including those who developed the PSQI, have
Front. Psychiatry 10:284. subsequently developed new measures; some of which utilize more modern standards for patient
doi: 10.3389/fpsyt.2019.00284 involvement and psychometric analysis (1, 3). The widespread adoption of the PSQI has led to a

Frontiers in Psychiatry | www.frontiersin.org 1 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

large literature that appears to facilitate comparison between classification of the sleep problems described in interviews,
samples, and now acts as a motivating factor for researchers to facilitate comparison of component and total PSQI scores,
and clinicians to continue to use the PSQI in preference of other with the clinical presentation as described in each participant’s
measures. This includes some populations for which it has not qualitative account (7).
been validated (4).
The PSQI is often used as a global measure of self-reported
sleep disturbance in people with schizophrenia spectrum RESULTS
disorders, but the validity of the PSQI (English version) as a
Fifteen participants were recruited, including acute inpatients
global measure of sleep disturbance in this population has, to our
(n = 2), outpatients receiving intensive (daily) support (n = 3),
knowledge, not been evaluated. We explored the content validity
those under Community Mental Health Teams (n = 8), and
of the PSQI for assessing patient-reported sleep quality and sleep
under outpatient clinic only (n = 2); none were currently in
disturbance in people with schizophrenia spectrum disorders.
paid employment. There were 10 males and 5 females, with a
mean age of 45.9 (SD = 10.55), diagnosed with schizophrenia
(n = 8), schizoaffective disorder (n = 6), and delusional
METHODS
disorder (n = 1). All were prescribed either one (n = 8) or
We recruited 15 adults with schizophrenia spectrum disorders, two antipsychotics (n = 7); dosages as a fraction of defined
who were in contact with specialist mental health services in daily doses (8) ranged from 0.36 to 5.5 (mean 2.19, SD 1.28).
the United Kingdom, and had a self-reported problem with GAF-F and GAF-S scores ranged from 38 to 85, and from 21
sleep initiation, maintenance, quality, timing, or refreshingness. to 80, respectively (mean 62.3, SD 12.16 and mean 47.7, SD
People whose predominant complaint was of parasomnia or 19.40, respectively). For itemized PSQI component scores
sleep apnea were not included, in order to focus on insomnia and and raw values, see Table 1. Overall, the areas in which these
circadian rhythm problems. All participants’ data are included participants scored higher (indicating worse problems) were
in the current analysis. Written informed consent was obtained sleep latency, sleep quality, and daytime dysfunction, while
after participants reviewed the participant information sheet and sleep duration scored very low (which should suggest minimal
had sufficient opportunity for further explanation or questions. problems). Table 2 shows summary statements describing
Ethical approval was obtained through the NHS Research Ethics the nature of sleep complaints described in interview, and
Committee Proportionate Review Service (14/NS/1085). a breakdown of participants endorsing various types of
Demographic data were collected, and symptoms and problems.
functioning were rated using the Global Assessment of
Functioning (GAF) split version (GAF-F and GAF-S). Acceptability
Participants completed the PSQI and were invited to report Most participants reported no problem completing the measure
their experience as they went through the questionnaire; this and felt it asked relevant questions. Although some noted a
was followed by an in-depth interview that further explored preference for open questions, this is not an issue specific to
their sleep experiences and complaints (see Supplementary the PSQI. A minority of participants suggested there should be
File S1). In addition to the planned questions, the interviewer more questions relating to psychological or mental health-related
used continuers and active listening techniques; interview causes of sleep disruption.
questions later went on to cover other research aims including
exploring acceptability of potential treatments, and barriers
to improving sleep; these results are reported elsewhere (5). Sleep Duration
The use of in-depth interview is an additional complementary Nine participants scored 0 for sleep duration; however, four
approach to quantitative psychometrics in evaluating the validity of these participants were sleeping 11 to 14.5 h, and expressed
of standardized self-report questionnaires, and it has been used concerns about this:
informatively to examine interpretation of other self-reported
“I’ve looked it up on Google and it says things like,
health measures (6).
a higher risk of heart attack, diabetes or early death
Transcription noted long pauses and we made field notes on
[laughs]. [ … ] I do feel guilty, quite a lot, yeah. I would
nonverbal expressions (e.g., frowning, and nonlexical utterances
like to be able to … I would love to be able to just be a
such as “Errrr…”). Analysis was facilitated by Nvivo (qualitative
morning person” (r05, reported sleep duration = 14.5 h,
analysis software), creating an audit trail, and ensuring themes
score on this item = 0)
were linked back to the data. Transcript content was coded in
relation to the PSQI question each section related to, and in Hypersomnia was seen as a potential health concern, and a
relation to emergent themes and subthemes from in-depth cause for negative self-concept:
analysis of participant interviews. The qualitative analysis used a
framework approach, and samples of the data were independently “you’re lazy … you’re wasting your life away” (r12).
analyzed by a second researcher to enhance reliability. The
mixing of methods was approached through qualitization of Participants who described a large amount of nightly variation
individual PSQI component scores, and summarizing and found average sleep duration difficult to calculate accurately:

Frontiers in Psychiatry | www.frontiersin.org 2 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

TABLE 1 | Participant itemized PSQI scores, hours of sleep, and minutes sleep latency.

Sleep disturbances1
Sleep latency: min/

Total PSQI score2

Use of sleeping
Hours of actual
sleep: h/score1

Habitual sleep

Self-reported
dysfunction1

medication1
efficiency1
Daytime

quality1
score1
Respondent

r01 11/0 60/3 0 0 0 0 0 3

r02 4.5/3 3/0 1 2 1 2 3 12
r03 12/0 10/0 1 2 0 0 3 6
r04 6/1 60/1 0 0 0 0 0 2
r05 14.5/0 180/3 1 3 0 1 0 8
r06 6.5/1 60/3 1 3 1 1 0 10
r07 4/3 120/3 1 1 2 2 3 15
r08 8.5/0 20/1 1 1 0 1 3 7
r09 11/0 30/2 2 1 1 1 0 7
r10 4.5/3 30/2 1 3 3 3 3 18
r11 8/0 30/1 1 0 1 1 0 4
r12 3/3 180/3 1 2 3 1 0 13
r13 8/0 60/3 1 0 0 2 3 9
r14 9/0 10/2 1 0 0 0 0 3
r15 7/0 60/3 2 2 1 2 3 13
Averages 7.83/0.9 61/2.0 1.0 1.3 0.9 1.1 1.4 8.7
Number of participants PSQI indicates have poor sleep quality = 11
1Minimum score = 0 (better), maximum score = 3 (worse). 2Minimum score = 0 (better), maximum score = 21 (worse), Total >5 associated with poor sleep quality. PSQI, Pittsburgh
Sleep Quality Index.

TABLE 2 | Qualitative summaries of participant’s description of their sleep problems.

Self-report regarding sleep r01 r02 r03 r04 r05 r06 r07 r08 r09 r10 r11 r12 r13 r14 r15

Frequent problem with long sleep latency1 x x x x x

Occasional severe problem with long sleep latency 1 x x x

Problem maintaining sleep or excessively early rising 1 x x x x x x x

Problem with difficulty rising or waking1 x x x x x x

Problem with too long sleep duration 1 x x x x

Unusually long sleep, not a problem at present 2 x x

Usually regularly naps2 x x x x x x x x

Problem with prolonged sleep inertia 1 x x x x x x x

Significantly troubled by bad dreams1 x x x x x x

1Items are selected where this was a major and consistent aspect of the participant’s self-reported complaint; items are only selected where the participant subjectively perceived
this as a problem.
2Items are selected where this was a frequent occurrence, may not subjectively be a problem.

“sometimes [waking up] will be 6 o’clock for like nights of getting almost no sleep at all, followed by very long
three weeks, but very rarely it’s 11 o’clock [ … ] if sleep when they did eventually sleep. These participants’ mean
I’m feeling too enthusiastic I’ll be awake all night total sleep time did not capture this issue as the very long and
because of the excitement from the day [ … ] yeah very short sleep times were averaged to a normal duration. Some
so it asks for a fixed time, but it’s quite hard to distinguished “actual sleep” from light sleep/partial sleep, so were
estimate, it varies a lot” (r02, reported average sleep unsure how best to respond. Some answers weren’t internally
duration = 4.5 h, score on this item = 3) consistent (e.g., time to bed till time to wake, minus sleep latency
and sleep interruptions, was inconsistent with reported total sleep
Seven of the 15 participants tried to give ranges, which were time). It should be acknowledged that the latter of these issues
sometimes several hours apart; three participants described could affect many retrospective self-report measures.

Frontiers in Psychiatry | www.frontiersin.org 3 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

It is important also to note that daytime naps are not endorsed 3× per week, but some described less frequent but
included within the sleep duration total, and for over half in intense bad dreams causing significant distress, which was not
this sample (eight participants), naps were a significant source well captured:
of sleep:
“Oh jeeze I’m always having bad dreams … I’d say
“Respondent: [ … ] I always go to sleep in the afternoon maybe twice a week.” (r12)

Interviewer: Most days? Significantly, in interview the vast majority of the sample
complained of problems with poor sleep maintenance and depth,
Respondent: Yeah I’d say every day. in terms of “broken” sleep, sleep that was “not deep,” or was not
“proper sleep”; however, the average score for sleep disturbance
Interviewer: How long for? was 1.0 (0 = best, 3 = worse). This can largely be attributed to
the aggregation of scores from physical and psychological causes
Respondent: One and a half to two hours” (r10,
of sleep disturbance where there are more physical causes listed.
reported sleep duration = 4.5 h, score on this item = 3)
It was noted that sleep, which was disturbed by a wide range
Other participants described 3- or 4-h naps; hence, the PSQI of causes, scored higher than sleep very often disturbed, but
total sleep time question missed roughly half of their actual total generally by the same cause. Comparison of individual accounts
sleep for that day. and sleep disturbance scores showed that sleep that felt broken,
but without a complete awakening, did not readily translate to a
high score for “sleep disturbance.”
Sleep Timing
Average sleep timings are measured by the PSQI, but do not
contribute directly to the score. The times recorded give useful “Another Reason…”
information for clinicians on circadian preference or social Although perhaps a trivial matter, the phrasing of this question
commitments when sleep timing is regular; in this group, proved problematic for well over half of participants, causing a
however, times varied and averages may be less meaningful. pause in completion and questions regarding either the first part
This variability may have been missed altogether if times were or both parts of this question:
averaged by participants without comment. Dissatisfaction
with sleep timing, and unpredictability of sleep timing, were “…but what does that mean, how often during the past
significant sources of dysfunction and distress in participant month have you had trouble sleeping because of this,
accounts; participants described the impact on their ability to because of what?” (r10)
take on work, education, or social commitments. Satisfaction
It was also noted that this question rarely elicited information,
with or regularity of sleep timing is not part of the PSQI
as participants brought up many “other reasons” in interview
scoring so a problem with sleep timing does not directly
(e.g., hypnopompic hallucinations), but wrote “N/A” on the
impact the score.
PSQI. This may contribute to the unusually low scores for sleep
disturbance, as these “other reasons” were not scored.
Sleep Latency
Sleep latencies reported in answering the PSQI and in interview
were similar. While it is interesting that some participants Daytime Dysfunction
had long sleep latency (60 min, score 3 = worst) and were The PSQI asks about trouble staying awake “while driving, eating
untroubled by this, this constitutes a quantitative aspect of meals, or engaging in social activity”; this question appeared
their sleep disturbance, which is accurately summarized by not to be sensitive to sleepiness in those who did not drive and
the PSQI. socialized infrequently:

“My sleep’s a bit spontaneous, my body don’t plan it [ …

Sleep Disturbance ] I’m always falling asleep watching films [ … ] but no,
It is not clear how decisions were made regarding what are I’m trying to think now how often I do a social activity,
considered normal frequencies for some of the listed types it’s less than once a week isn’t it. So it’s less than once a
of sleep disturbance, resulting in floor and ceiling effects. week isn’t it falling asleep.” (r15, score on this item = 0)
Participants who described “problems” with going to the
bathroom at night went several times per night, the highest Many asked if falling asleep in front of the television counted,
option to select being ×3 per week. Someone who woke to and some then answered yes for this question.
use the toilet twice a week explained that they felt this was The other question concerns “enthusiasm to get things
probably less than most people. With regards to the impact done”; some noted they had difficulty with enthusiasm due to
of bad dreams, it seemed that frequency of bad dreams bore mood or psychotic symptoms, rather than their sleep. Daytime
limited relation to the distress caused; in this sample, no one dysfunction questions did not pick up on the impact on daytime

Frontiers in Psychiatry | www.frontiersin.org 4 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

functioning, where participants were napping or sleeping for Interviewer: What?

excessive periods to counter tiredness:
Respondent: Like, when they say have a nice sleep
“I’m really fed up because I’d like to get out and do and you’ll feel refreshed and all this nonsense.
things instead of sleeping the days away” (r01, daytime
dysfunction score = 0) Interviewer: They say that.

“It can be as short as half an hour or as long as two Respondent: Yes, and I don’t feel like that.
hours [ … ] I go to sleep because I’m tired in the
day time, not because I’m bored.” (r14, daytime Interviewer: No.
dysfunction score = 0)
Respondent: I feel like, jeez, what’s happened?” (r12,
Sleep inertia and difficulty waking were also major complaints sleep quality rated “fairly good” = 1)
discussed by participants within the current study (n = 6 of 15).
In the context of the rest of the analysis (5), this can be attributed
These should be detected as a form of daytime dysfunction;
to lowered expectations, so “fairly good” could mean good—
however, half of those expressing this complaint scored 0 for
when all is considered, good—compared to others with the same
daytime dysfunction (see Tables 1 and 2).
condition. It is also possible that participants responded regarding
sleep quality by evaluating individual periods of sleep obtained,
Sleep Efficiency in contrast to the adequateness of their day-to-day sleep as a
Sleep efficiency has been found to be lower on average in groups whole. Potentially also more rapport was built during the in-depth
with schizophrenia (9); in this sample, average sleep efficiency interview and participants felt more open and prepared to describe
score does not suggest that this was a particular difficulty problems.
(average = 0.9). Interview accounts described difficulties initiating
sleep, or maintaining sleep, suggesting poor sleep efficiency. Of Sleeping Medication
those who reported one or more of these difficulties (n = 11), the The present sample’s highest scoring domain was use of sleeping
average sleep efficiency score was 1.09; only four reporting such medication. This did not, however, represent high levels of
complaints scored 0. This suggests that the sleep efficiency score hypnotic use in this sample; in six out of seven of those scoring
detected relevant problems to some extent in most cases. 3 (highest), their answer related to their oral antipsychotic being
“sleeping medication” (although some felt this was an ineffective
Quality sleeping medication). Some described in interview using their
Interestingly, over half of participants rated quality as very good antipsychotic to control their sleep onset, but answered “never”
(0) or fairly good (1), but went on to state significant concerns to this question on the PSQI, and some raised the dilemma of
with their sleep and its impact on their life, including that their whether their antipsychotic counted or not. Answers were
sleep was not restorative, that their poor sleep pattern was a therefore dictated by semantic interpretation rather than any
barrier to getting a job, or that their sleep was “medicated sleep” meaningful differences between perceptions or behaviors.
and therefore substandard:

“[If I wasn’t on medication] That I’d actually sleep,

Sleep Disordered Breathing
The PSQI includes questions regarding snoring or breathing
yeah. And I think I’d be able to do more things as well,
among its sleep disturbance questions, and also a section
you know, in the day, if I wasn’t on the medication,
for completion by the person’s bed partner/roommate to
sometimes, if I managed to get natural sleep.” (r03,
screen for sleep disordered breathing, in acknowledgement
sleep quality rated “very good” = 0)
of people’s reduced awareness of their own breathing during
For some, there seemed to be a direct contradiction between sleep. Participants in this study did endorse snoring, but rarely
self-reported “sleep quality” on the PSQI and their view of their endorsed “cannot breathe comfortably,” rather clarifying that
sleep during interview: they breathed heavily, not had difficulty breathing:

“Interviewer: …how would you describe your sleep, if “…cause I’m a big lad as well so when I’m lying down
you were sort of telling someone about it? … I’d say not it’s hard to breathe but I breathe heavily.”
(r15, cannot breathe comfortably = 1, cough or snore
Respondent: Umm, not very good. loudly = 3, circled ‘loudly’ for emphasis).

Interviewer: No? It was never designed as such, and it is important that the
PSQI is not considered to be an effective screening for sleep
Respondent: No. Not like other people … go on like disordered breathing, particularly without the bed partner/
sleep’s supposed to be, you know? roommate questions being completed.

Frontiers in Psychiatry | www.frontiersin.org 5 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

Total Scores low regarding sleeping medication, perhaps owing to different

The total PSQI scores indicated that seven participants were either phrasing in the translation (14).
good sleepers or had only mild sleep problems (n = 4 score <5, Insufficient detection of problems with sleep depth is
n = 3, score 6–7). Of these seven, four described significant and significant particularly for this population, for whom levels
severe concerns during interview, while the other three described of shallow sleep (stage 1) are often elevated, and deeper sleep
milder but definite problems. Of those whose PSQI scores suggested (Stage 2 and Stage 3 non-REM sleep) is often reduced (9). Although
moderate or severe problems (score 8–18), the global impression objective assessment of sleep depth requires polysomnography or
from the interview was also of moderate or severe problems. spectral analysis, the experience of deep sleep was important to
participants. Even apart from importance to individuals, subjective
evaluations of sleep have often been found to be equally if not
DISCUSSION more predictive of health and functioning outcomes than some
more objective measures (15, 16), suggesting even “inaccurate”
The sample reported multiple and complex problems with sleep experiences may be equally important to capture.
initiation, continuity, quality, and timing, with attendant daytime Our findings are consistent with those of Waters et al. (12) who
dysfunction; the PSQI was capable to assess some, but not all, of these found only small and statistically nonsignificant differences in PSQI
issues. The PSQI appeared to be suitable for identifying self-reported scores between people with schizophrenia and healthy controls, but
short sleep, long sleep latency, or complete awakenings during the found increased variability in sleep latency, efficiency, and duration
night, but poorly represented some other problems such as variable in schizophrenia when using actigraphy. Actigraphy or sleep diaries
and inconsistent sleep length, poor sleep depth or quality, increased can be recommended to assess variability. However, retrospective
sleep inertia, hypersomnia, and inappropriate or inconsistent sleep self-report is less burdensome and has the potential to offer some
timing. While issues with sleep timing are beyond the intended insight; a future measure might include questions that assess how
scope of the PSQI, sleep duration, quality, and daytime dysfunction frequently various sleep values deviate from the average, by more
are within its scope and were poorly captured. Furthermore, it is than a certain amount (e.g., “How many times in the last month?
common for total PSQI scores to be treated as a global measure of was it 2 h more or less than this?”). Appropriate phrasing, format,
sleep disturbance, which these findings suggest is not valid. Reliance and content would require development and testing.
on total PSQI score as a measure of sleep dysfunction is particularly
inappropriate for those with schizophrenia spectrum disorders
whose sleep problems include more circadian dysregulation than Clinical Assessment of Sleep
other groups (10), and who as a result experience more inconsistent For current clinical practice, supplementary questions or additional
and variable sleep, and more difficulties timing sleep patterns to fit measures should be used when using the PSQI as a screening
with life expectations (5, 11, 12). Some of the measurement issues for sleep problems. For instance, the PSQI should not be relied
highlighted also have potential implications for interpretation of upon to screen for sleep disordered breathing; a ready alternative
PSQI scores in other populations. is the STOP-Bang questionnaire, which has been found to be
reasonably accurate in detection (17) and is freely available and
Measuring Sleep Duration, Variability, brief (18). Measures of circadian preference might be added (19,
20); however, these do not measure regularity of rhythm. It is
and Depth possible to measure and quantify regularity of rest-activity rhythms
As some participants feared, both excessively short and excessively
through actigraphy, describing both amplitude (relative amplitude)
long sleep are indeed associated with increased mortality (13),
and regularity of rhythm (interday stability) (21), as has been
and it has previously been recommended that the relationship
more extensively utilized in samples with dementia (22) who also
of sleep duration to assumed sleep quality on the PSQI should be
experience circadian dysregulation. At least one retrospective self-
U-shaped and not linear (14). Our findings support this suggestion,
report measure of regularity is available [e.g., (23)], although none
concurring that unusually long sleep, as well as too short sleep,
has yet been tested in schizophrenia spectrum disorders. During
caused concerns for participants. It is also important to note that
clinical interview, therefore, additional questions are recommended
in people taking significant naps, as was common in this sample,
regarding regularity of sleep timing, and the match between sleep
the PSQI can mischaracterize (underestimate) a person’s total sleep
timing and individual lifestyle choices and requirements.
time, as might also occur in regional populations in whom biphasic
sleep is common. These issues with calculation and scoring of sleep
duration of course affect the use of the PSQI in many other clinical Outcome Measurement
and nonclinical samples, not just in those with schizophrenia Whether for research or clinical outcome measurement for quality
spectrum disorders. improvement, the findings of the present study caution against
Participant PSQI scores were similar to those from research relying on the PSQI total score alone, as improvements in sleep timing
with the Japanese version of this instrument in a similar sample or regularity (often accompanied by improved quality of life and
(14), where sleep latency, sleep quality, and daytime dysfunction functioning) may go undetected. There are more recently developed
received higher scores on the PSQI, while sleep duration scored very tools, including the PROMIS sleep dysfunction item bank (1), and
low [which should suggest minimal problems; Doi et al. (14) also the Glasgow Sleep Impact Scale (3), which have been specifically
noted hypersomnia was not captured]. In contrast to our study, the designed to act as a barometer of the patient’s perceived standard
subgroup of the Japanese sample with schizophrenia (n = 24) scored of sleep. Both tools were developed with patient involvement and

Frontiers in Psychiatry | www.frontiersin.org 6 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

have undergone validation in healthy controls and those with sleep or combined cause and nature, which could be used trans-
disorders, or in insomnia, respectively. These measures are very diagnostically. A future measure could attempt also to take into
promising and may offer a useful adjunct to clinical assessments of account different environmental contexts; for instance, in many
sleep issues for people with schizophrenia spectrum disorders, and, institutional settings, patients may more commonly go “to bed”
by virtue of their use of modern psychometric methods, may also far in advance of intending to sleep, as their bedroom may be the
offer a reliable means of comparison across diagnostic groups. only private space in which to wind down for sleep. This can lead to
These tools, however, are designed to measure change underestimation of sleep efficiency, as has previously been noted in
for research or clinical outcome measurement; they do not relation to sleep diaries (24); and alternative phrasing around “into
simultaneously help to characterize the sleep problem—as bed” has been recommended. There may also be utility in a measure
might be desired by a clinician. And in this respect, they that examines or considers the impact of a mismatch between
do not replace the PSQI. Asking the patient to specify sleep environment, occupational routine, and the individual, upon sleep,
latency, sleep times, and causes of sleep disturbance, as the as well as factors that are more inherent to the person.
PSQI does, can help identify the problem and therefore direct
treatment. Unfortunately, the PSQI alone is likely to give an
incomplete and sometimes misleading picture, in the case of
Self-Report Items versus Self-Evaluated
people with schizophrenia spectrum disorders, and possibly Items
many other groups. The PSQI is of course not unique among self-report measures in
being affected by participants calibrating some of their responses
in relation to their own context and peer group, as we found here
Limitations and Future Directions regarding rating of sleep quality. Similar findings of peer group-
The generalizability of the findings from a small sample might dependent evaluations were presented by Adamson et al. (6)
be questioned, although as the types of problems described are regarding the evaluation of general health:
similar to those found in larger samples studied using quantitative
methodologies, we believe these findings are transferable. Although “Mrs K: Oh, I suppose for my age my health is
the diversity in the type and extent of problems is potentially excellent., I mean to say, it wasn’t until I went up for
representative of the diverse problems experienced in this group, it the assessment I knew there was anything wrong with
also limits the number of cases with each particular type of problem my heart” [(6), p142]
(e.g., with short sleep, or with hypersomnia). Furthermore, diversity
in the environmental context of the participants, particularly This context-dependent evaluation may equally measure
the inclusion of both inpatients and outpatients, complicates a difference in a person’s perceived peer group, as much
interpretation. It would also have been useful to find out the as based on a change in self-perceived sleep, and makes it
approximate length of time since diagnosis, and length of time difficult to use exclusively self-evaluated items to compare
on antipsychotic medication, to better describe the sample and between populations. It may therefore be desirable to include
facilitate comparison with other studies. In hindsight, it would also some quantitative self-report elements, which are more
have been useful if participants had been asked to comment on the influenced by the individual’s perception of their sleep than
recommended interpretation of their component or total PSQI contextual factors.
scores (for instance, “This score suggests overall you have good/
slightly disturbed/severely disturbed sleep. Do you agree?”), which
might have provided a further point of reference.
CONCLUSION
This study did not set out to make statistical analysis of sensitivity Future research should develop a valid and reliable tool, with
or specificity, but these findings suggest a hypothesis of too low a similar shared utility for both clinicians and researchers as
sensitivity, and missed cases, but no issues with overdetection. the PSQI has uniquely offered; this shared utility no doubt
Future studies comparing PSQI to other measures such as facilitates understanding between clinicians and researchers,
actigraphy or polysomnography might confirm or quantify this, and and accounts for its enduring popularity. The authors suggest
could further examine which types of problem are underdetected the development of a new measure that can act as a clinical
in a larger sample. More detailed description of the weaknesses this screening and initial interview, and as an outcome measure
study has highlighted would support improved interpretation of the in research.
considerable body of important work, which has used the PSQI to
describe their sample or to measure change.
Our analysis demonstrates that the PSQI is insensitive to some ETHICS STATEMENT
sleep issues, which are described as important to people with
schizophrenia spectrum disorders. This disparity between the range Ethical approval was obtained through the NHS Research Ethics
of issues highlighted in our interviews and those covered by the Committee Proportionate Review Service (14/NS/1085), North
PSQI may suggest a need for a disease-specific measure to achieve of Scotland Research Ethics Committee 1. Written informed
high sensitivity to the particular problems of this group. Another consent was obtained after participants reviewed the participant
possibility is the development of a measure of sleep disturbance, information sheet and had sufficient opportunity for further
which can equally measure sleep problems of circadian, insomniac, explanation or questions. A disclosure or risk protocol and a distress

Frontiers in Psychiatry | www.frontiersin.org 7 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

protocol were followed during data collection, and information ACKNOWLEDGMENTS

sharing with care providers was discussed with participants in
advance (information was shared on participant’s request, or if any Professor Penny Bee (School of Health Sciences, University
immediate risks necessitated information sharing). of Manchester) is acknowledged for academic supervision
and support of SF during study design, data collection, and
analysis. Mr. Vik Veer [ENT Consultant, at Royal National
AUTHOR CONTRIBUTIONS Throat Nose & Ear Hospital, University College London
Hospitals NHS Foundation Trust (UCLH), Sleep Surgery
SF designed and conducted the study, collected and analyzed the Department] is acknowledged for input regarding discussion
data, and wrote the first draft of the manuscript. SF and CS-G of screening and assessment of sleep disordered breathing.
were involved in editing, conceptual formulation, and discussion The participants are thanked for their efforts in describing
of the findings and implications of the study. their experiences.

FUNDING SUPPLEMENTARY MATERIAL

This work was supported by the National Institute of
The Supplementary Material for this article can be found online at:
Health Research (NIHR), through funding support received
https://www.frontiersin.org/articles/10.3389/fpsyt.2019.00284/
independently by SF and CS-G during completion of this
full#supplementary-material
study. The NIHR had no direct involvement in study design,
conduct, or dissemination. FILE S1 | Question schedule and optional prompts.

REFERENCES 10. Pritchett D, Wulff K, Oliver PL, Bannerman DM, Davies KE, Harrison PJ,
et al. Evaluating the links between schizophrenia and sleep and circadian
1. Buysse DJ, Yu L, Moul DE, Germain A, Stover A, Dodds NE, et al. rhythm disruption. J Neural Transm (2012) 119(10):1061–75. doi: 10.1007/
Development and validation of patient-reported outcome measures for s00702-012-0817-8
sleep disturbance and sleep-related impairments. Sleep (2010) 33(6):781– 11. Waite F, Evans N, Myers E, Startup H, Lister R, Harvey AG, et al. The
92. [online]. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/ patient experience of sleep problems and their treatment in the context of
PMC2880437 doi: 10.1093/sleep/33.6.781 current delusions and hallucinations. Psychol Psychother: Theory Res Pract
2. Buysse DJ, Reynolds CF 3rd, Monk TH, Berman SR, Kupfer DJ. The Pittsburgh (2015) 89:181–93. [online]. Available from: http://doi.wiley.com/10.1111/
Sleep Quality Index: a new instrument for psychiatric practice and research. papt.12073 doi: 10.1111/papt.12073
Psychiatry Res (1989) 28(2):193–213. [online]. Available from: http://www. 12. Waters F, Sinclair C, Rock D, Jablensky A, Foster RG, Wulff K. Daily
ncbi.nlm.nih.gov/pubmed/2748771 doi: 10.1016/0165-1781(89)90047-4 variations in sleep-wake patterns and severity of psychopathology: a pilot
3. Kyle SD, Crawford MR, Morgan K, Spiegelhalder K, Clark AA, Espie CA. study in community-dwelling individuals with chronic schizophrenia.
The Glasgow Sleep Impact Index (GSII): a novel patient-centred measure Psychiatry Res (2011) 187(1–2):304–6. [online]. Available from: http://www.
for assessing sleep-related quality of life impairment in insomnia disorder. ncbi.nlm.nih.gov/pubmed/21272939 [Accessed October 28, 2014]. doi:
Sleep Med (2013) 14(6):493–501. doi: 10.1016/j.sleep.2012.10.023 10.1016/j.psychres.2011.01.006
4. Garrow AP, Yorke J, Khan N, Vestbo J, Singh D, Tyson S. Systematic literature review 13. Cappuccio FP, D’Elia L, Strazzullo P, Miller MA. Sleep duration and all-cause
of patient-reported outcome measures used in assessment and measurement of mortality: a systematic review and meta-analysis of prospective studies. Sleep
sleep disorders in chronic obstructive pulmonary disease. Int J Chron Obstruct (2010) 33(5):585–92. [online]. Available from: http://www.pubmedcentral.
Pulmon Dis (2015) 10:293–307. [online]. Available from: http://www.scopus. nih.gov/articlerender.fcgi?artid=2864873&tool=pmcentrez&rendertype=ab
com/inward/record.​url?eid=2-s2.0-84922743032&partnerID=tZOtx3y1 stract doi: 10.1093/sleep/33.5.585
5. Faulkner S, Bee P. Experiences, perspectives and priorities of people 14. Doi Y, Minowa M, Uchiyama M, Okawa M, Kim K, Shibui K, et al.
with schizophrenia spectrum disorders regarding sleep disturbance Psychometric assessment of subjective sleep quality using the Japanese
and its treatment: a qualitative study. BMC Psychiatry (2017) 17(1):158. version of the Pittsburgh Sleep Quality Index (PSQI-J) in psychiatric
[online]. Available from: DOI 10.1186/s12888-017-1329-8 doi: 10.1186/ disordered and control subjects. Psychiatry Res (2000) 97:165–72. doi:
s12888-017-1329-8 10.1016/S0165-1781(00)00232-8
6. Adamson J, Gooberman-Hill R, Woolhead G, Donovan J. ‘Questerviews’: using 15. Harvey AG, Tang NKY. (Mis)perception of sleep in insomnia: a puzzle and
questionnaires in qualitative interviews as a method of integrating qualitative and a resolution. Psychol Bull (2012) 138(1):77–101. [online]. Available from:
quantitative health services research. J Health Serv Res Policy (2004) 9(3):139–45. http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=3277880&tool=
[online]. Available from: http://www.ncbi.nlm.nih.gov/pubmed/15272971 pmcentrez&rendertype=abstract [Accessed October 22, 2014]. doi: 10.1037/
[Accessed November 4, 2014]. doi: 10.1258/1355819041403268 a0025730
7. Migiro SO, Magangi BA. Mixed methods: a review of literature and the future 16. Pilcher JJ, Ginter DR, Sadowsky B. Sleep quality versus sleep quantity:
of the new research paradigm. Afr J Bus Manage (2011) 5(10):3757–64. [online]. relationships between sleep and measures of health, well-being and
Available from: http://www.academicjournals.org/AJBM sleepiness in college students. J Psychosom Res (1997) 42(6):583–96. doi:
8. WHO. WHO Collaborating Centre for Drug Statistics Methodology., p. 10.1016/S0022-3999(97)00004-4
ATC/DDD Index. [online]. Available from: https://www.whocc.no/atc_ 17. Abrishami A, Khajehdehi A, Chung F. A systematic review of screening
ddd_index/ [Accessed March 12, 2017]. questionnaires for obstructive sleep apnea. Can J Anaesth (2010) 57(5):423–
9. Chan MS, Chung KF, Yung KP, Yeung WF. Sleep in schizophrenia: a 38. doi: 10.1007/s12630-010-9280-x
systematic review and meta-analysis of polysomnographic findings in case- 18. Chung F, Subramanyam R, Liao P, Sasaki E, Shapiro C, Sun Y. STOP-Bang
control studies. Sleep Med Rev (2017) 32:69–84. [online]. Available from: doi. Questionnaire. Toronto: Toronto Western Hospital (2018). [online]. Available
org/10.1016/j.smrv.2016.03.001 doi: 10.1016/j.smrv.2016.03.001 from: http://www.stopbang.ca/osa/screening.php [Accessed August 1, 2018].

Frontiers in Psychiatry | www.frontiersin.org 8 May 2019 | Volume 10 | Article 284

Faulkner and Sidey-Gibbons PSQI Is Problematic in Schizophrenia

19. Roenneberg T, Wirz-Justice A, Merrow M. Life between clocks: daily 23. Monk TH, Buysse DJ, Kennedy KS, Pods JM, DeGrazia JM, Miewald JM.
temporal patterns of human chronotypes. J Biol Rhythms (2003) 18(1):80– Measuring sleep habits without using a diary: the sleep timing questionnaire.
90. doi: 10.1177/0748730402239679 Sleep (2003) 26(2):208–12. doi: 10.1093/sleep/26.2.208
20. Randler C, Díaz-Morales JF, Rahafar A, Vollmer C. Morningness–eveningness 24. Carney CE, Buysse DJ, Ancoli-israel S, Edinger JD, Krystal AD, Lichstein
and amplitude—development and validation of an improved composite scale KL, et al. The Consensus Sleep Diary: standardizing prospective sleep
to measure circadian preference and stability (MESSi). Chronobiol Int (2016) self-monitoring. Sleep (2012) 35(2):287–302. doi: 10.5665/sleep.1642
33(7):832–48. [online]. Available from: http://dx.doi.org/10.3109/07420528.201
6.1171233 doi: 10.3109/07420528.2016.1171233 Conflict of Interest Statement: The authors declare that the research was
21. Van Someren EJW, Swaab DF, Colenda CC, Cohen W, McCall WV, conducted in the absence of any commercial or financial relationships that could
Rosenquist PB. Bright light therapy: improved sensitivity to its effects be construed as a potential conflict of interest.
on rest-activity rhythms in Alzheimer patients by application of
nonparametric methods. Chronobiol Int (1999) 16(4):505–18. doi: Copyright © 2019 Faulkner and Sidey-Gibbons. This is an open-access article
10.3109/07420529908998724 distributed under the terms of the Creative Commons Attribution License (CC BY).
22. Gonçalves BSB, Adamowicz T, Louzada FM, Moreno CR, Araujo JF. A fresh The use, distribution or reproduction in other forums is permitted, provided the original
look at the use of nonparametric analysis in actimetry. Sleep Med Rev author(s) and the copyright owner(s) are credited and that the original publication in
(2015) 20:84–91. [online]. Available from: http://dx.doi.org/10.1016/j. this journal is cited, in accordance with accepted academic practice. No use, distribution
smrv.2014.06.002 doi: 10.1016/j.smrv.​2014.​06.002 or reproduction is permitted which does not comply with these terms.

Frontiers in Psychiatry | www.frontiersin.org 9 May 2019 | Volume 10 | Article 284