Neurobiology of Schizophrenia
Schizophrenia
Features
o Schizophrenia affects the most basic human processes of perception, emotion, judgement
o Heterogenous syndrome
o No single defining symptom or sign
o Currently cannot be identified with a diagnostic laboratory test
o Diagnosis:
Psychotic phenomena – hallucinations, delusion and thought disorder – after other causes of
psychosis have been excluded
Symptoms
o Positive symptoms – characterised by abnormal thoughts, perceptions, language and behaviour
Include
Delusions
o False beliefs or thoughts with no basis in reality
Hallucinations
o Disturbances of sensory perception – e.g. seeing, hearing, feeling things that
are not there
o Auditory and visual hallucinations
Disorganised thinking / speech
o Jumping from topic to topic, slipping off topic, responding to questions with
unrelated answers, speaking incoherently
Disorganised behaviour
o Problems performing goal directed daily activities like meal planning and
maintaining personal hygiene, child-like actions, unprovoked agitation
Lack of insight
o Individuals unaware that their delusions or hallucinations aren’t real –
distressing
Positive symptoms can also be characterised as symptoms of psychosis
Symptoms of psychosis
o Delusions
o Hallucinations
o Disorganised thinking/ speech
o Disorganised behaviour
o Lack of insight
Causes of psychosis
o Schizophrenia – more likely to have persecutory delusions
o Bipolar disorder – during episodes of mania + more likely to have grandiose
delusions
o Severe stress/anxiety
o Severe depression
o Postnatal psychosis – 1:1000
o Lack of sleep
o Encephalitis
o Substance misuse
o Can also occur in several medical conditions – AD, PD, malaria,
hypoglycaemia, MS, brain tumour
o Negative symptoms – characterised by restrictions in range and intensity of emotional expression,
communication, body language and interest in normal activities
Blunted (flat) effects
, Neurobiology of Schizophrenia
Decreased emotional expressiveness, unresponsive immobile facial appearance,
reduced eye contact and body language
Alogia
Reduced speech, responses are curt and detached, speech may be less fluid
Avolition
Lacking motivation, spontaneity, initiative
o E.g. sitting for length periods or ceasing to participate in work or daily
activities
Anhedonia
Lacking pleasure or interest in activities that were once enjoyable
o Cognitive symptoms
Subtle cognitive problems are increasingly recognised as central to the disease
Include
Impairments in attention, working memory, learning, verbal fluency, motor speed,
executive functions
o Poor working memory
Linked to dysfunction of the dorsolateral prefrontal cortex
Even patients with good performance are inefficient in their use of
prefrontal networks
Cognitive deficits are relatively stable + already apparent in first-episode patients
Leads to impairment of skills and diminished functional capacity
Also found in biological relatives of subjects
Suggesting that the aspect of cognitive impairment in SCZ – may be under genetic
control
Cognitive tests could be used in clinical trials and genetic testing
Diagnosing schizophrenia
o Criteria for schizophrenia – from the diagnostic and statistical manual of mental disorders 5 th edition
(DSM5)
A
2 or more of the following symptoms for >1 month unless treated successfully –
include:
o Delusions, hallucinations, disorganised speech, disorganised or catatonic
behaviour, + negative symptoms – such as affective flattening or loss of
initiative
B
Level of functioning is significantly decreased in work, personal relationships, and/or
personal care
C
Symptoms of the disorder last >6 months
D
Exclusion of schizo-affective disorder, unipolar and bipolar effective disorder
E
Symptoms cannot be attributed to the use of drugs or medication, or to a somatic
disorder
F
In the case of pre-existing autism spectrum disorder – at least 1 month with
prominent hallucinations or delusions
Treating schizophrenia (psychosis) by targeting the dopamine pathway
o Dopamine hypothesis of SCZ
Derived in part from the discovery of anti-psychotics in the 50s
D2 dopamine receptor is the main target of antipsychotics
