Schizophrenia Flashcards
What is schizophrenia?
A psychotic disorder involving disturbance of thought, emotion and behaviour.
What are the symptoms associated with schizophrenia?
Positive symptoms (excess or distortion):
Disorganised speech
Hallucinations
Delusions
Negative symptoms (behavioural deficits):
Avolution (lack of energy and inability to persist in routine activities)
Alogia (reduction in amount/content of speech)
Anhedoia (severe impairment in social relationships)
What are the causes of schizophrenia?
Genetic predisposition Neurodevelopment abnormalities Biochemical abnormalities Pre-morbid personality Environmental factors
What genetic factors cause schizophrenia?
Schizophrenia is common in families, with first degree relatives of a sufferer having a 10x higher chance of developing the condition, although this may be due to a shared environment. However twin studies show genes have a higher influence as monozygous twins have a concordance of 48% whereas dizygotic twins have only 10%.
Research sugests there is not a single disease causing gene, but a number of different genes that interact with each other and the environment to cause the disease.
Genes that have shown to be involved in the development of schizophrenia include:
Neuregulin 1
Disrupted-in-schizophrenia (DISC1)
Dysbindin 1
How do neurodevelopment abnormalities cause schizophrenia?
The neurodevelopmental hypothesis of schizophrenia states schizophrenia is a result of a pathological process that begins very early in life and results in abnormal development of the central nervous system.
Studies of adult patients with schizophrenia show low childhood IQ, poor performance at school, behavioural and motor abnormalities (clumsiness and ambidextrousness) and language difficulties.
Post-mortem and neuroimaging studies show increased ventricular spaces and reduced cortical volumes. Difference sin the hippocampus and its connections to the frontal lobe have also been observed.
The hypofrontality hypothesis postulates that positive symptoms are associated with increased activity in the left hippocampal region and negative symptoms are associated with decreased activity in frontal areas.
What biochemical abnormalities can cause schizophrenia?
Increased dopamanergic, glutamatergic and serotonergic transmission and decreased GABAergic transmission may play a role in schizophrenia pathogenesis.
What treatment is available for schizophrenia?
Typical antipsychotics are D2 receptor antagonists, and are effective in two thirds of schizophrenia patients.
Cognitive behavioural therapy has shown to be effective. It involves helping patients to cope with chronic hallucinations and delusions.
What is the dopamine theory of schizophrenia?
The observation that amphetamine (displaces dopamine from presynaptic terminals, increasing synaptic dopamine availability) can produce auditory hallucinations led to the theory that schizophrenia is caused by increased dopaminergic transmission. Increased D2 recepotrs are found in schizophrenic brains.
Further studies have shown mesolimbic hyperactivity result in positive symptoms, but mesocortical hypoactivity cause negative symptoms.
What is the glutamate theory of schizophrenia?
Administration of an NMDA receptor antagonist induces schizophrenic like symptoms and exacerbates existing symptoms, suggesting NMDA hypofunction is a potential mechanism underlying schizophrenia.
Studies show NMDA binding and glutamate levels are reduced in schizophrenic brains.
What is the serotonergic theory of schizophrenia?
The 5-HT hypothesis is based on 2 major types of psychedelic hallucinogenic drugs, which act through 5-HT2A receptors.
Polymorphisms of the 5-HT2A receptor gene is reported as a minor risk
What environmental factors can cause schizophrenia?
Obstetric complications have shown to increase risk of schizophrenia, including problems during pregnancy, labour or foetal development.
Low socio-economic status is associated with schizophrenia, however it is unsure whether this is a cause or consequence.
Heavy cannabis use, particularly use in early teenage years has shown an increase in the development of schizophrenia.
