Chapter 16 - Schizophrenia and Affective disorders Flashcards
serious mental disorder characterized by disordered thoughts, delusions, hallucinations, and often bizarre behaviors
schizophrenia
Refers to the breakdown of integration of emotion, thought, and action
“Splitting of psychic functions”
Diagnosis of schizophrenia
The recurrence of only 2 symptoms for one month
1 symptom is necessary if the person exhibits delusions that are particularly bizarre or hallucinations that include 1 voice providing a running commentary or 2 voices conversing
Type of schizophrenia. Not as bad. Does not mean you will always have schizophrenia.
acute
– gradual onset, progressive deterioration
~ 1/3 of those diagnosed will show progressive deterioration
Chronic schizophrenia
: statistic which gives an estimate of the total variance in a trait that is attributable to genetic variation in a group
Heritability
Mechanisms that control the expression of genes
Epigenetics
Antipsychotic drug side effects suggests role for dopamine – drugs work by decreasing dopamine levels; positive symptoms of schizophrenia are associated with dopamine overactivity
Reserpine depletes brain of dopamine and other monoamines by making vesicles leaky
Amphetamine, cocaine and L-dopa are dopamine agonists and produce psychosis
Dopamine Theory of Schizophrenia
Major CNS dopaminergic systems include
Nigrostriatal System (role in movement) Mesolimbic System (role in reinforcement/reward) Mesocortical System (role in short-term memory, planning, and problem solving)
Activation of D1-like Rs
stimulates cAMP
Activation of D2-like R
inhibits cAMP
All DA receptors are
metabotropic
Anti-Schizophrenic Drugs
2 Classes
Phenothiazines
Butyrophenones
drug that Binds to D1 & D2 Receptors
Chlorpromazine
drug that bind to d2 receptors only
Spiroperidol
Revised DA Theory of Schizophrenia
Schizophrenia is caused by hyperactivity at D2 Rs, rather than DA Rs in general
1) Based on 2 findings:
2) Selective binding of butyrophenones to D2 Rs
Butyrophenones greater potency in the clinic.
Brains of schizophrenics have an abnormally high # of D2 Rs
Higher level of occupancy of those Rs by DA
Suggest both pre & postsynaptic abnormalities
long term side effect of using anti-psychotic drugs
Tardive Dyskinesia Tardus – slow Dyskinesia- faulty movement Late-developing TD: unable to stop moving Supersensitivity: possible that DA receptors become hypersensitive if they are blocked for long periods of time D2 receptors in caudate and putamen
Problems with the D2 Theory
Schizophrenia associated with brain damage
Little damage to dopamine circuitry
Damage not explained by dopamine theory
It takes several weeks of neuroleptic therapy to alleviate schizophrenic symptoms
Conventional neuroleptics (D2 blockers) mainly effective for positive symptoms
Negative and cognitive symptoms might be caused by brain damage
May be best to think of schizophrenia as multiple disorders with multiple causes
Schizophrenia as a neurological disorder Predisposing factors (genetic, environmental, or both) give rise to
Abnormalities in both DA transmission and PFC
Abnormalities in DA transmission that cause abnormalities in PFC
Abnormalities in PFC cause abnormalities in DA transmission
Schizophrenia: Brain Abnormalities
Evidence of brain damage
Negative and cognitive symptoms
Loss of brain tissue
Lateral ventricles more than twice as large in schizophrenic patients than control subjects
Possible Causes of Brain Abnormalities
Epidemiological Studies Season of birth Viral epidemics Population density Prenatal malnutrition Maternal stress
Age of Onset for schizophrenia
Symptoms rarely begin before late adolescence or early adulthood