Gene-Environment Interaction and Mental Disorders

Five HTTLPR Gene and Depression

• The five HTTLPR gene regulates serotonin reuptake and has two variants:
  • Long form
  • Short form
• Individuals with the short form allele may have increased risk of depression when combined with stressful life events.
• The interplay of genetics (gene type) and environment (stressful events) is crucial; it's not a direct cause-effect relation.

Interaction Between Genetics and Environment

• Stressful life events (e.g., loss of a loved one) amplify the likelihood of depressive episodes, particularly for those with the short gene variant.
• Graph visualization shows:
  • Short (homozygous) allele in red
  • Heterozygous (one short, one long) in green
  • Long form (homozygous) in blue
• Increased risk of depression becomes pronounced with higher numbers of stressful events (especially beyond 3 events).

Gene Environment Interaction Study

• A study revealed higher rates of chronic depression in adults with a short allele, especially those exposed to maltreatment in childhood.

Understanding Schizophrenia

• Symptoms of Schizophrenia:
  • Hallucinations: Perceptual experiences without external stimuli (e.g., hearing voices)
  • Delusions: Strong beliefs contrary to reality (e.g., paranoid delusions, grandiosity)
  • Disorganized Thinking: Difficulty organizing thoughts, which affects actions.
  • Negative Symptoms: Absence of normal emotions or behaviors (e.g., lack of motivation, emotional expression, and speech).

Schizophrenia: Overview

• Diagnosed typically after psychosis onset (late teens to early thirties).
• Positive Symptoms: Include hallucinations and delusions.
• Negative Symptoms: Reduce emotional range, motivation, and cognitive functions.

Causes and Treatment of Schizophrenia

• Multiple Causes: Likely a combination of genetic predispositions and environmental triggers (e.g., drug use, early exposure to viruses).
• Treatment:
  • Traditional antipsychotics target dopamine receptors (effective for positive symptoms) but may worsen negative symptoms.
  • Newer antipsychotics aim to balance neurotransmitter activity.
  • Cognitive behavioral therapy and early interventions can improve outcomes.

Dissociative Disorders vs. Schizophrenia

• Dissociative Disorders: Characterized by detachment from self or reality.
• Dissociative Amnesia: Rare, often following traumatic experiences; memory loss with no prior neurological issues.
  • Depersonalization/Derealization Disorder: Recurring feelings of unreality towards self (depersonalization) or the world (derealization).
• Dissociative Identity Disorder (DID): Extremely rare; involves multiple distinct identities, often rooted in traumatic experiences.

Personality Disorders

• Characteristics: Inflexible patterns that differ from cultural norms, causing distress or impairment.
• Types of Personality Disorders:
  • Borderline Personality Disorder: Instability in relationships, self-image, and intense emotions; often associated with previous trauma.
  • Antisocial Personality Disorder: Disregard for others' rights, with impulsive and often illegal behaviors; lack of empathy and remorse.
• Prevalence: Approximately 9% of the population with varying types, with borderline and antisocial being more prevalent and problematic.

Violence and Mental Illness

• Mental disorders are rarely linked to violence; most people with mental illnesses are nonviolent and frequently victims of violence.
• Substance abuse increases risks; assessing mental competence in legal contexts is complex.

Key Terms to Remember

• Gene-Environment Interaction: Intersection of genetic predisposition and environmental stressors leading to depression.
• Positive Symptoms (Schizophrenia): Symptoms present when they shouldn’t be (e.g., hallucinations).
• Negative Symptoms (Schizophrenia): Symptoms indicating absence of expected behaviors (e.g., lack of motivation).
• Dissociative Identity Disorder: Rare disorder characterized by the presence of multiple identities, often linked to trauma.