Week 10 - Schizophrenia Flashcards
(14 cards)
Schizophrenia symptoms
Three categories of symptoms: negative, cognitive and positive.
Symptom onset is usually in early adulthood but can happen earlier or later
Appear gradually, over a period of 3-5 years.
Negative symptoms are the first to emerge, followed by cognitive symptoms. The positive symptoms emerge last.
Positive symptoms
Thought Disorders:
- disorganized irrational thinking
- great difficulty logically arranging thoughts
- etc
Delusions:
- persecution - false beliefs that others are plotting and conspiring against oneself.
- grandeur - false beliefs about one’s power and importance (godlike powers, special knowledge that no one else possesses)
- control - related to persecution i.e the person believes that he or she is being controlled by others through radar or a tiny radio receiver implanted in his or her brain.
Hallucinations - Auditory and Olfactory, can happen in more senses too
Negative Symptoms
Known by the absence or diminution of normal behaviors:
- flattened emotional response
- poverty of speech
- lack of initiative
persistence - anhedonia
- social withdrawal
Cognitive Symptoms
- difficulty in sustaining attention
- low psychomotor speed (the ability to rapidly and fluently perform movements of the fingers, hands, and legs)
- deficits in learning and memory
- poor abstract thinking
- poor problem solving
- all associated with frontal lobe hypofunction - hypofrontality
- lower performance on stroop task and Wisconsin card sort test
Other difficulties/ brain structural differences
Sensory-motor gating deficits – difficulties screening out irrelevant stimuli and focusing on salient ones
Lack smooth pursuit in tracking a moving stimulus - oculomotor function
- reduced brain volume in temporal, frontal lobes, and hippocampus
- enlargement of lateral ventricles (twice as big as normal)
Heritability and Genetics
- is a heritable trait, multiple genes involved, e.g. DISC1
- The children of older fathers are more likely to develop schizophrenia. - mutations in spermatocytes
dichorionic - twins in womb with individual placenta
monochorionic - twins in womb sharing a single placenta - higher rate of schizophrenia
Neurodevelopmental Theories
The ‘late’ neuro - developmental model:
- schizophrenia may result from an abnormality or deviation in adolescence, when synaptic pruning takes place
“Two-hit” model:
- Atypical development in schizophrenia takes place during 2 critical time points:
- early brain development and adolescence.
- During adolescence, excessive synaptic pruning and loss of plasticity
Neurochemistry: The Dopamine (DA) Hypothesis
Proposes the schizophrenia is caused by abnormalities in DA functioning in the brain
- Overactivity of DA in the mesolimbic system results in the positive symptoms of schizophrenia
- Underactivity of DA in the mesocortical system results in the negative and cognitive symptoms of schizophrenia
DA agonists produce symptoms that resemble the positive symptoms of schizophrenia - amphetamine, cocaine, methylphenidate and L-DOPA.
chlorpromazine CPZ is a DA antagonist – first antipsychotic
Treatment with antipsychotics and side effects
These drugs eliminate, or at least diminish the positive symptoms in most of the patients. About 20-30% do not respond to these drugs
Long-term treatment leads to at least some symptoms resembling those in Parkinson’s disease: slowness in movement, lack of facial expression, and general weakness.
A more serious side effect develops in ~1/3 of all patients who took the drugs for an extended period: tardive dyskinesia - patients with tardive dyskinesia are unable to stop moving.
Newer Drugs
Atypical Antipsychotics
Atypical antipsychotics work in treatment-resistant patients
Atypicals do not have the Parkinsonian side-effects due to the fact that they have lower affinity for the D2 receptors
Improve both positive and negative symptoms of schizophrenia
Also improve the performance in neuropsychological tests which is not the case with typical antipsychotics
Clozapine - also reduces suicidality - very poor side affects
The Glutamate Hypothesis of Schizophrenia
Glutamate is the major excitatory neurotransmitter in the central nervous system and the most prevalent one
Evidence implicates NMDA receptors in schizophrenia - NMDA responsible for most all neuro-development processes
Schizophrenia is due to NMDA receptor hypofunction
This theory is more comprehensive - it can explain the positive, negative & cognitive symptoms of schizophrenia
Neuroinflammatory hypothesis of schizophrenia
The brain’s immune cells are hyperactive in people who are at risk of developing schizophrenia
Oestrogen (estrogen) Hypothesis of Schizophrenia
Lack of estrogen, as it seems to be a buffer for schizophrenia
Summary
Schizophrenia is a syndrome involving a variety of symptoms and elusive aetiology
Typical antipsychotic drugs are only partly effective - DA hypothesis
Atypical antipsychotics address both positive and negative symptoms of schizophrenia especially clozapine
A faulty glutamate system (NMDA R) may better explain schizophrenia symptoms and account for DA disparities in the brain (Glutamate hypothesis)
Acquired immunity may bring all the evidence together into one major explanation for schizophrenia
