PSYCHOBIOLOGY OF PSYCHIATRIC DISORDERS Flashcards
(15 cards)
WHAT IS A NEURO TRANSMITTER?
- CHEMICAL MESSENGER THAT TRANSMITS SIGNALS BETWEEN NERVE CELLS (NEURONS) IN BRAIN AND BODY
-REGULATES MOOD THOUGHT PROCESS AND BEHAVIOUR
KEY NEUROTRANSMITTERS
SEROTONIN - MOOD REGULATION- LINKED TO DEPRESSION
DOPAMINE - PLEASURE, ATTENTION - LINKED TO SCHIZOPHRENIA
GABA- CALMING - LINKED TO ANXIETY
DISORDERS OVERVIEW
Schizophrenia: hallucinations, delusions, brain structure differences.
Depression: low mood, low energy, serotonin imbalance.
Anxiety disorders: overactive brain areas, low GABA.
PSYCHOBIOLOGY
- REFERS TO THE STUDY OF THE BIOLOGICAL FOUNDATIONS OF BEHAVIOUR AND MENTAL PROCESSES, ESPECIALLY HOW THE BRAIN AND NERVOUS SYSTEM INFLUENCE PSYCHIATRIC DISORDERS
PSYCHIATRIC DISORDER DEFINED AS…
as a mental condition characterized by disturbances in thoughts, emotions, or behaviors, which cause significant distress or impair daily functioning.
KEY BIOLOGICAL FACTORS IN PSYCHIATRIC DISORDERS
- NEUROTRANSMITTERS
-CHEMICAL MESSAGERS IN BRAIN THAT TRANSMIT SIGNALS BETWEEN NEURONS
- IMBALANCES ARE LINKED TO SPECIFY PSYCHATRIC DISORDERS:
1)SEROTONIN - DEPRESSION, ANXIETY, OCD
2)DOPAMINE - schizophrenia (excess), Parkinson’s (deficiency), addiction
3) GABA → anxiety disorders (low levels = increased excitability).
4) Glutamate → schizophrenia, depression.
BRAIN STRUCTURE AND FUNCTION
Structural abnormalities in brain regions linked to specific disorders:
Amygdala → emotion regulation, anxiety.
Hippocampus → memory, mood disorders.
Prefrontal cortex → decision-making, executive function, schizophrenia, depression.
Neuroimaging (fMRI, PET scans) shows functional differences in psychiatric patients.
GENETICS
Hereditary factors contribute to vulnerability.
Twin, family, and adoption studies show higher concordance rates in genetically related individuals.
Example: Schizophrenia has a concordance rate of around 50% in identical twins.
Endocrine (Hormonal) Factors
Endocrine (Hormonal) Factors
HPA Axis (Hypothalamic-Pituitary-Adrenal axis) regulates stress responses.
Overactivation linked to depression and anxiety.
Hormonal imbalances (thyroid, cortisol) can trigger or worsen mental disorders.
NEURODEVELOPMENTAL FACTORS
Early brain development issues due to:
Prenatal infections
Birth complications
Childhood trauma
Linked to autism spectrum disorders, ADHD, and schizophrenia.
PSYCHOPHARMACOLOGY
Psychopharmacology
Medications target neurotransmitter systems to correct imbalances.
Antidepressants (SSRIs, SNRIs) → increase serotonin/noradrenaline.
Antipsychotics → reduce dopamine activity.
Anxiolytics (benzodiazepines) → enhance GABA effects.
CONCLUSION
The psychobiology of psychiatric disorders highlights how biological systems — including neurotransmitters, brain structures, genetic inheritance, and neurodevelopmental factors — contribute to the onset, maintenance, and treatment of mental illnesses.
While biological explanations offer valuable insights and treatment pathways, most psychiatric disorders are multifactorial, meaning psychological and social influences also play a significant role.
NEUROTRANSMITTER ROLES
& LINKED DISORDERS
- Serotonin
role- regulates, mood, sleep, appetite and emotion,
linked disorders - low levels linked to depression & anxiety disorder
2.Dopamine
Role- reward motivation, attention and movement
Linked Disorders - excess activity - linked to schizophrenia - deficiency to Parkinson disease
3.GABA (Gamma-Aminobutyric Acid)
Role- Major inhibitory neurotransmitter- reduces neuronal excitability
Linked Disorder - low level linked to anxiety
Neurotransmitters & Psychiatric Disorders (50 marks)
Introduction
- Define neurotransmitters: chemical messengers in the brain that transmit signals between neurons.
State their importance in regulating mood, behavior, and cognition.
- Introduce the idea that imbalances or dysfunctions in neurotransmitters are linked to various psychiatric disorders.
- Briefly outline key neurotransmitters to be discussed: serotonin, dopamine, GABA, and noradrenaline.
- State that you will also consider strengths, limitations, and alternatives (like psychological factors).
1️⃣ Serotonin and Depression
AO1 (Knowledge)
Explain serotonin’s role in regulating mood, sleep, and emotion.
The serotonin hypothesis suggests low levels cause depressive symptoms.
AO3 (Evaluation)
✅ Supported by effectiveness of SSRIs (Selective Serotonin Reuptake Inhibitors) in treating depression.
❌ Not all patients respond to SSRIs; depression is likely multifactorial.
❌ Causation issue — unclear if low serotonin causes depression or is a result of it.
✅ Brain imaging shows lower serotonin activity in some depressed individuals.
2️⃣ Dopamine and Schizophrenia
AO1
Dopamine hypothesis: excess dopamine in the mesolimbic pathway causes positive symptoms (hallucinations, delusions).
Low dopamine in the mesocortical pathway may cause negative symptoms (flat affect, withdrawal).
AO3
✅ Supported by antipsychotic drugs (e.g., chlorpromazine) that block dopamine receptors and reduce positive symptoms.
❌ Newer theories suggest involvement of other neurotransmitters (like glutamate).
❌ Some patients show little dopamine abnormality.
✅ Revised dopamine hypothesis recognises regional dopamine imbalances.
3️⃣ GABA and Anxiety Disorders
AO1
GABA is the brain’s main inhibitory neurotransmitter — calms neural activity.
Low GABA linked to anxiety disorders, as lack of inhibition leads to overactivity in fear circuits (e.g. amygdala).
AO3
✅ Benzodiazepines (which enhance GABA) effectively reduce anxiety symptoms.
❌ Risk of dependence and side effects limits use.
✅ Supported by neuroimaging studies showing reduced GABA in anxious individuals.
4️⃣ Noradrenaline and Stress/Depression
AO1
Noradrenaline involved in the stress response and mood regulation.
Low levels linked to depression; high levels to anxiety and stress disorders.
AO3
✅ Some antidepressants (SNRIs) increase noradrenaline levels.
❌ Complexity — interacts with other neurotransmitters, so effects aren’t straightforward.
✅ Helps explain physical stress symptoms (increased heart rate, arousal).
5️⃣ Broader Evaluation
Reductionist: focusing solely on neurotransmitters ignores psychological, social, and environmental factors.
Interactionist (biopsychosocial) model better explains disorders as resulting from biological vulnerability + life events.
Diathesis-stress model: genetic/biological predisposition triggered by environmental stress.
Conclusion
- Neurotransmitters clearly play a crucial role in psychiatric disorders, with strong evidence from pharmacological treatments and neuroimaging.
- However, no single neurotransmitter explains a disorder alone.
- Best understood within a biopsychosocial framework, combining biological, psychological, and social factors.
Biological explanations for schizophrenia (50 MARK)
INTRO: DEFINE SCHIZOPHRENIA
-SYMPTOMS: POSITIVE: HALLUCINATIONS, DELUSIONS/NEGATIVE: FLAT AFFECT, SOCIAL WITHDRAWAL
INTRODUCE BIOLOGICAL EXPLANATION = FOCUS ON GENETICS, NEUROTRANSMITTERS, AND BRAIN STRUCTURE ABNORMALITIES.
OUTLINE AREAS TO BE DISCUSSED
1) GENETIC EXPLANATION
-SCHIZOPHRENIA HAS A GENETIC BASIS - RUNS IN FAMILLIES .
TWIN STUDIES: HIGHER CONCORDANCE IN MONOZYGOTIC TWINS VS DIZYGOTIC TWINS. ADOPTION STUDIES = HIGHER RISK IN BIOLOGICAL RELATIVES OF SCHIZOPHRENICS, EVEN RAISED APART
A03(EVALUATION): STRONG EVIDENCE, GENE MAPING BUT CONCORDANCE IN MZ NOT 100% & SCHIZOPHRENIA = LIKELY POLYGENIC
2) DOPAMINE HYPOTHESIS
-SUGGESTS EXCESS DOPAMINE ACTIVITY
-HYPERACTIVITY IN MESOLIMIBIC PATHWAY = LINKED TO HALLUCINATIONS AND DELUSIONS
-NEWER VERSION INCLUDE LOW DOP IN MESCOCORTIAL PATHWAY
-SUPPORTED BY EFFECTIVENESS OF ANTIPSYCHOTICS & BRAINIMAGING
BUT SOME SHOW NORMAL DOP LEVEL AND BRAIN IMAGING SHOWS INCREASED DOP ACTIVITY
3) BRAIN STRUCTURE ABNORMALITIES
-MRI& CT SCAN = PHYSICAL DIFFERENCE IN SCHIZO BRAINS
FINDINGS:
1)ENLARGED VENTRICLES
REDUCED GREY MATTER IN PRE-FRONTAL CORTEX
ABNORMALITIES IN THE HIPPOCAMPUS AND AMYGDALA
A03
-Consistent imaging evidence in chronic patients.
-Not all with these abnormalities have schizophrenia.
-Cause or consequence? Changes may result from long-term illness or medication.
Overall Evaluation
Biological explanations are reductionist — ignore psychological and social influences.
Interactionist approach better: combines biological vulnerability and environmental stressors (e.g. trauma, urban living, drug use).
The Diathesis-Stress Model integrates these, offering a more complete account.
Conclusion
Biological explanations provide strong evidence for genetic, neurochemical, and structural causes of schizophrenia.
No single factor alone is sufficient.
The most comprehensive understanding comes from combining biological findings with psychological and environmental perspectives.
