Causal Factors

The Biological Perspective

- The traditional biological viewpoint considers mental disorders as diseases with primary
symptoms that are cognitive, emotional, or behavioral, rooted in the central nervous
system, autonomic nervous system, and/or endocrine system, either inherited or caused
by pathological processes. Initially, simple biological explanations were sought, but now
it's recognized that explanations are rarely simple and psychological and sociocultural
factors also play significant roles.
- Neurological Diseases and Brain Damage: The first disorders recognized with biological
components involved gross brain tissue destruction, resulting in neurological diseases.
These disrupt brain functioning physically or biochemically, causing psychological or
behavioral aberrations. For example, brain damage can lead to memory loss or
depression.
- Non-Neurological Mental Disorders: Most mental disorders do not result from brain
damage but from abnormalities in neurotransmitter systems. Delusions and hallucinations
in disorders like schizophrenia are not directly caused by brain damage but involve
complex neural integration influenced by personality and learning.
- Categories of Biological Factors:
- Genetic Vulnerabilities: Inherited predispositions to certain mental disorders.
- Brain Dysfunction and Neural Plasticity: Changes in brain structure and function
that can influence behavior and mental health.
- Neurotransmitter and Hormonal Abnormalities: Imbalances in chemicals within
the brain and central nervous system that affect mental states.
- Temperament: Innate traits that influence how individuals respond to their
environment.

Genetic Vulnerabilities

Introduction
The genetic basis of mental disorders involves the interplay of inherited genetic factors and
environmental influences. Genes, composed of DNA, are located on chromosomes within the
cell nucleus and exist in alternate forms called alleles. While no single gene fully determines the
development of a mental disorder, substantial evidence suggests that genetic factors contribute
significantly to the vulnerability to these disorders. This interplay can influence traits and
behaviors that predispose individuals to mental health issues.

The Relationship of Genotypes to Phenotypes

● Genotype: The total genetic makeup of an individual, encompassing all inherited genes.
 ● Phenotype: The observable characteristics of an individual that result from the interaction
of the genotype with the environment. This includes physical traits, behaviors, and
psychological characteristics.
● Polygenic Inheritance: Mental disorders are rarely caused by single genes but by multiple
genes or gene polymorphisms. These genes collectively contribute to structural
abnormalities in the central nervous system, neurotransmitter imbalances, and hormonal
irregularities.

Genotype-Environment Interactions

● Concept: Genetic factors do not act in isolation but interact with environmental factors to
influence the development of mental disorders. This interaction is crucial in
understanding why certain individuals develop mental disorders while others do not.
● Diathesis-Stress Model: Proposes that a genetic predisposition (diathesis) combined with
environmental stressors can trigger mental disorders.
● Examples:
● PKU (Phenylketonuria): Children with a genetic inability to metabolize
phenylalanine can develop intellectual disabilities if exposed to phenylalanine in
their diet.
● Depression: Individuals with certain genetic variants (e.g., serotonin transporter
gene) are more likely to develop depression in response to stressful life events.

Genotype-Environment Correlations

● Passive Effect: The environment provided by genetically related parents is influenced by

their own genetic makeup, which can enhance a child's genetic predispositions (e.g.,
intelligent parents creating a stimulating environment for a child).
● Evocative Effect: A child's genetically influenced behaviors evoke specific responses
from the environment (e.g., a musically talented child receiving special opportunities).
● Active Effect (Niche Building): Individuals actively seek out environments that
complement their genetic tendencies (e.g., an extroverted child seeking social
interactions).

Methods for Studying Genetic Influences

1. Family History (Pedigree) Method:

● Involves examining the incidence of a disorder among relatives of a proband to
assess genetic contributions.
 ● Limitation: Relatives often share environments, making it difficult to separate
genetic and environmental effects.
2. Twin Method:
● Compares concordance rates of disorders between monozygotic (MZ) twins (who
share 100% of their genes) and dizygotic (DZ) twins (who share about 50% of
their genes).
● Higher concordance rates in MZ twins compared to DZ twins suggest a genetic
influence.
● Limitation: Identical twins may be treated more similarly than fraternal twins,
potentially confounding results.
3. Adoption Method:
● Studies individuals adopted at birth to separate genetic from environmental
influences.
● Compares the incidence of disorders in adopted-away offspring of biological
parents with a disorder to those without.
● Higher rates of disorders in the biological relatives suggest a genetic influence.

Separating Genetic and Environmental Influences

● Shared Environmental Influences: Factors that make family members similar, such as
shared household characteristics or common family experiences.
● Nonshared Environmental Influences: Unique experiences that differentiate individuals
within the same family, such as differential parental treatment or unique personal
experiences at school.
● Importance: Nonshared influences often have a greater impact on individual differences
in behavior and psychopathology than shared influences.

Linkage Analysis and Association Studies

1. Linkage Analysis:
● Identifies the chromosomal location of genes related to mental disorders by
tracking genetic markers within families.
● Relies on known genetic markers (e.g., eye color) to infer the location of genes
related to mental disorders.
● Challenges: Replicating results is difficult due to the polygenic nature of most
disorders.
● Examples: Potential gene locations for bipolar disorder (chromosome 11) and
schizophrenia (chromosomes 22, 6, 8, and 1).
2. Association Studies:
 ● Compare the frequency of genetic markers between groups with and without a
disorder.
● Identify genes associated with disorders by noting markers that occur more
frequently in affected individuals.
● Example: Higher frequencies of markers related to dopamine functioning in
children with hyperactivity suggest genes involved in hyperactivity are located
near these markers.
● Promise: More effective for identifying small effects of specific genes in
polygenic disorders.

Conclusion

The genetic basis of mental disorders involves complex interactions between multiple genes and
environmental factors. While traditional methods like family, twin, and adoption studies provide
valuable insights into genetic influences, advanced techniques like linkage analysis and
association studies offer promising avenues for identifying specific genetic factors.
Understanding these interactions can lead to better prevention and treatment strategies for mental
disorders.

Brain Dysfunction and Neural Plasticity

- Advances in understanding the role of brain dysfunction and neural plasticity in mental
disorders have expanded rapidly in recent decades, aided by sophisticated neuroimaging
techniques. While specific brain lesions rarely directly cause psychiatric disorders, subtle
deficiencies in brain structure or function are increasingly recognized as contributing
factors. Genetic factors play a significant role in guiding brain development, yet the
process is not rigid or deterministic; rather, there exists considerable neural
plasticity—the brain's ability to adapt and change in response to various experiences and
stimuli.
- Positive prenatal experiences, such as enrichment during pregnancy, have been linked to
offspring showing resilience to early brain injury. Conversely, negative prenatal
experiences, like exposure to unpredictable loud sounds, can lead to neurochemical
abnormalities in infants. Postnatal environmental factors also significantly impact brain
development. For instance, experiences during infancy and childhood profoundly affect
the formation of neural connections, or synapses, with enriched environments promoting
thicker cell development and more synapses per neuron.
- Physical exercise, such as running, has been shown to stimulate neurogenesis, the
creation of new brain cells, even in older animals. This highlights the ongoing neural
plasticity throughout the lifespan. Research on neural and behavioral plasticity, combined
 with the understanding of genotype-environment correlations, underscores the
importance of a developmental systems approach in developmental psychopathology.
- This approach recognizes the bidirectional influences between genetics, neural activity,
behavior, and the environment. It acknowledges that genetic factors influence neural
activity, which in turn affects behavior, and vice versa. Furthermore, environmental
factors, including physical, social, and cultural influences, also shape behavior and neural
activity, potentially influencing genetic activity as well. Overall, this perspective
emphasizes the dynamic and interactive nature of the developmental process in shaping
mental health outcomes.

Imbalances of Neurotransmitters and Hormones

- Effective communication between neurons relies on neurotransmitters, chemical

substances released into the synapse—the space between neurons. Nerve impulses trigger
the release of neurotransmitters from the presynaptic neuron, which then bind to receptor
sites on the postsynaptic neuron, either stimulating or inhibiting impulse transmission.
These neurotransmitters are either quickly destroyed by enzymes or reabsorbed into the
presynaptic neuron.
- Imbalances in neurotransmitter systems are implicated in abnormal behavior, although
they are only part of the causal pattern for most disorders. Excessive production,
dysfunctions in deactivation processes, or receptor sensitivity issues can all lead to
neurotransmitter imbalances. Different disorders are associated with specific patterns of
imbalances in neurotransmitter systems.
- Key neurotransmitters studied in relation to psychopathology include norepinephrine,
dopamine, serotonin, glutamate, and GABA. Medications used to treat disorders often
target neurotransmitter systems, aiming to correct imbalances. For instance,
antidepressants like Prozac and Zoloft prolong the presence of serotonin in the synapse.
- Hormonal imbalances are also linked to certain forms of psychopathology. Hormones,
chemical messengers secreted by endocrine glands, influence various physiological
processes, including fight-or-flight reactions and sexual responses. The
hypothalamic-pituitary-adrenal (HPA) axis plays a crucial role in stress regulation, with
malfunctions implicated in disorders like depression and posttraumatic stress disorder.
Additionally, sex hormones from gonadal glands contribute to behavioral differences
between genders and can influence maladaptive behavior when imbalanced.
 Temperament

- Temperament encompasses a child's reactivity and ways of self-regulation, believed to be

biologically programmed. It manifests in emotional and arousal responses, influencing
approach, withdrawal, and attention to stimuli. Genetic factors strongly influence
temperament, but prenatal and postnatal environments also play a role.
- Around 2 to 3 months of age, five dimensions of temperament emerge: fearfulness,
irritability/frustration, positive affect, activity level, and attentional persistence/effortful
control. These dimensions correspond to adult personality traits like neuroticism,
extraversion, and constraint. Boys tend to show higher activity levels, while girls often
demonstrate greater impulse control and attention regulation.
- Temperament stability varies but can influence developmental processes significantly.
For instance, fearful temperament can lead to fear conditioning and avoidance behaviors,
while positive affect and high activity levels correlate with mastery motivation. Children
with high negative emotionality may challenge parental support, especially in lower
socioeconomic status families.
- Temperament also shapes susceptibility to psychopathology. Behaviorally inhibited
children, prone to fear and hypervigilance, are at risk for anxiety disorders later in life.
Conversely, highly uninhibited children may struggle with learning moral standards and
exhibit aggressive behavior later on, especially when combined with hostility,
predisposing them to conduct disorder and antisocial personality disorder.

The Impact of the Biological Viewpoint

- The biological perspective has significantly influenced our understanding of human

behavior, highlighting the role of biochemical factors and innate characteristics, many of
which are genetically determined, in both normal and abnormal behavior. However,
several misconceptions exist regarding the interpretation of biological discoveries.
- Establishing biological differences between individuals with and without certain
disorders does not automatically classify those disorders as illnesses. Clinical judgment
regarding the functional effects of disordered behavior, specifically whether it leads to
significant distress or impairment in functioning, is crucial in determining mental illness.
- While all thoughts, feelings, and behaviors occur as biological events in the brain, they
are also influenced by social events in the environment. Thus, understanding abnormal
behavior requires integrating multiple perspectives, including biological, psychological,
and sociocultural factors.
- Moreover, mental disorders are often intertwined with individuals' personalities and the
challenges they face in their lives. Therefore, integrating various perspectives into a
biopsychosocial framework is essential for a comprehensive understanding of
psychopathology.