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Schizophrenia: Risk Factors, Explanations + Prognosis - Coggle Diagram
Schizophrenia: Risk Factors, Explanations + Prognosis
Prognosis:
- ~ 45% schizophrenia cases recover after 1/more episodes
- ~ 20% show constant symptoms + increased disability
- ~ 35% display varied degrees of progress/deterioration
- Extremely high suicide rate:
Nannerz et al (2001) - 30% schizophrenic patients attempted suicide at least once during lifetime
Radomsky et al (1999) - 10% of schizophrenic people die by suicide
Genetic/Familial Factors
- Risk of developing schizophrenia <1% in general population
- Risk of developing schizophrenia 2-9% if first degree relatives
- Risk of developing schizophrenia 1.5-3% if second degree relatives
- Rudin (1916) - Schizophrenia tends to cluster in families
Twin Studies:
- MZ twins = ~ 50% concordance rate
- DZ twins = 4% concordance rate
- Suggests genetic link, but also other factors involved (e.g. environment)
Dysfunctional families
Gregory Bateson
- 'Double Bind' (say something but expect the opposite)
E.g. Complain about lack of affection but push away child when trying to hug
Dysfunctional families: Hirsch + Leff (1974)
- Compared parents of schizophrenic patients with parents of people with other disorders
- More communication deviance in parents of schizophrenic patient
- Small no. of parents spoke much
- When communication was controlled, no difference between groups
Leff + Vaughan (1976)
- Recruited patients on admission + followed up on discharge
- Observed families in naturalistic settings
- Recorded + transcribed communication
- Rated each for expressed emotion
- Found: Patients in high expressed emotion families showed high relapse rate 1 year after discharge
- Strength: Replicated many times
- Limitation: Direction of causality unknown
Stress + Pregnancy
- Can interfere with foetal brain development
- High risk of child developing schizophrenia in women:
- Whose partner died during pregnancy (Huttunen, 1989)
- Affected by battle/war during pregnancy (Van Os + Selten, 1998)
Perinatal Complications:
- Babies experienced birth complications = 2x as likely to develop schizophrenia (Cannon, 1997; Jones, 1998)
- Birth complications lead to hypoxia (lack of oxygen in organs + tissues)
Miller et al (2001)
- Compared life events of schizophrenic ppts + non-schizophrenic ppts
- High risk ppts with more life events = greater risk of developing schizophrenic symptoms
- Minor life events not significantly associated with schizophrenic symptoms
- Limitation: Causation problem - life events = symptoms, or vice versa?
Recreational drug use
Drugs inducing psychosis include:
- Amphetamine (speed)
- Cocaine
- LSD
- Ketamine
- Cannabis (associated with schizophrenia)
Miller et al (2001):
- Compared cannabis use in ppts who developed schizophrenic symptoms + ppts who didn't
- Cannabis is a risk factor for developing psychotic symptoms in vulnerable young people
Di Fortio et al (2015):
- Compared 410 patients with 1st psychotic episode with 370 controls between 2005-2010
- 2.9x higher risk of developing psychotic disorder for cannabis users
- 5.4x higher risk of developing psychotic disorder for skunk users
- ~ 1/4 of 1st psychotic episodes due to skunk use
Life Expectancy:
- Worse than smoking
- Years lost = 15-20 years
- Unknown cause
Environmental Factors
- Similar representation + prevalence worldwide = widespread environmental factors
- Typically develops in early adulthood = environmental role during development
Retrospective studies:
- Ask parents/family about child's early life
- Compare patients to control ppts
Follow-back studies:
- Use objective evidence (e.g. medical records) to find out about child's early life
High risk studies:
- Select sample of ppts at high risk of developing schizophrenia
- Follow them prospectively before they develop schizophrenia
- Compare those who do develop schizophrenia with those who don't + controls
Retrospective studies limitations:
- Selective + incomplete recall
- Search after meaning - Look for particular instances to explain condition
- Expensive to conduct widescale study
Follow-back studies limitations:
- Objective evidence often sparse/missing/lost/not detailed
Eve Johnstone et al (1999) High risk study:
- Followed up 155 ppts aged 16-24 at risk of getting schizophrenia
- Compared to 36 controls
- Estimated risk of developing schizophrenia = 10-15%
Psychosocial environment
Urban upbringing
- Being socially isolated increases risk of developing schizophrenia
Kirkbride et al (2014):
- Incidence of non-affective psychosis affected by inequality, absolute deprivation, population density
- For Black Caribbeans + Black Africans, risk was associated with ethnic separation, ethnic density
Dopamine
Original dopamine hypothesis:
- Excessive dopamine activity = positive symptoms of schizophrenia
- 'Typical' anti-psychotics block dopamine receptors
- Explains Parkinsonian side effects of treatment + psychotic side effects of treating Parkinson's Disease
- Limitation: Doesn't explain negative symptoms of schizophrenia
Revised dopamine hypothesis:
- Overactivity of dopamine Mesolimbic pathway = Positive symptoms
- Both typical + atypical anti-psychotics:
- Block dopamine
- Reduce mesolimbic activity
- Reduce positive symptoms
- Underactivity of dopamine mesocortical pathway = Negative symptoms
- Atypical anti-psychotics:
- Block serotonin
- Reduce inhibition of mesocortical pathway
- Increase mesocortical activity
- Reduce negative symptoms