38- Schizophrenia Flashcards
what is schizophrenia?
complex mental disorder where people interpret reality abnormally
name the three types of symptoms
positive
negative
cognitive
examples of positive symptoms of schizophrenia?
hallucinations = perceptions experienced without stimulus, often auditory
delusions = strong held false beliefs not consistent with the norm/reason, often paranoid
thought disorders - disorganised thought/speech
movement disorders
examples of negative symptoms?
social withdrawal, impaired social functioning
anhedonia = decreased ability to experience pleasure
lack of motivation
emotional flatness
examples of cognitive symptoms?
impaired memory, attention, comprehension
tend to appear later on in life
describe the effects of thought disorders
positive symptoms of schiz. associated with disordered thought and speech
thought disorders - disturbances in thinking
- unintelligible speech, distorted and illogical
- failure to follow through with a train of thought
name the four phases of schizophrenia?
prodromal
acute
remission
relapse
describe the four phases of schizophrenia
- prodromal = initial signs - sleep disturbances, unusual behaviour, social withdrawal. often triggered by stress.
- acute = manifestation of psychotic positive symptoms - hallucinations, delusions, disordered thinking. can last 4-6 weeks, often results in diagnosis and hospitalisation
- remission = symptoms subside, return to ‘normal’
- relapse = return or worsening of symptoms following remission
cycling through the phases can last for a variable period of time - weeks, months or years
describe the cause of schizophrenia
no true single cause for schizophrenia - often an interplay between environmental and genetic factors
genetic:
- risk increases with a family history
- gene deletions/mutations of candidate genes can affect risk = interplay of multiple genes can trigger schiz., but having the genes doesn’t guarantee having schiz.
environmental:
- pregnancy
- stress in life
- early life stresses = premature birth, asphyxia birth
- malnutrition or viral infections
- drug use - e.g. cannabis and LSD induce hallucinations
describe the dopamine theory behind schizophrenia
mesocortical pathway associated with motivation, cognitive control and emotional response. mesolimbic pathway induces reward
- hyperactivity, increased D2 receptor activity = positive symptoms (delusions, hallucinations, disrupts thinking)
- hypoactivity, decreased D1 receptor activity = negative symptoms (social withdrawal, emotional flatness)
pharmacological evidence - amphetamine increases dopamine release and produces behavioural changes that resemble schizophrenia
D2 receptor blockers - antipsychotic drugs - are affective in alleviating positive symptoms = supports the link between dopamine neurotransmission dysfunction and schizophrenia
imaging studies show an increase in dopamine receptor density in schizophrenics - inconsistent finding
evidence against the dopamine theory
no changes in CSF fluid between schizophrenics and healthy patients for HVA concentration - HVA is a metabolite of dopamine
inconsistent findings with imaging studies and increased dopamine receptor density, and for dopamine release in response to amphetamine
how do brain structure differences explain the pathophysiology of schizophrenia?
- overall smaller brain size
- enlarged ventricles
- atrophy of the amygdala and hippocampus
- hypofrontality = reduced blood flow and activity of the prefrontal cortex, which is involved in decision-making, cognitive function and emotional expression; dysfunction linked to negative symptoms.
describe how glutamate & NMDA receptor dysfunction could explain the pathophysiology of schizophrenia
NMDA receptor dysfunction affects glutamate neurotransmission as a major excitatory NT
- decrease in glutamate levels and NMDA function in prefrontal cortex of schizophrenics
- transgenic mice with this show stereotyped behaviour and negative symptoms
NMDA antagonists - e.g. ketamine - can induce psychotic symptoms like hallucinations and thought disorders
how is 5-HT implicated in the pathophysiology of schizophrenia?
LSD as a partial 5-HT agonist induces hallucinations - related to 5-HT receptor activation
oxidative stress in the pathophysiology of schizophrenia
increased oxidative stress contributing to neuronal damage and dysfunction
