Genetic Causes (biological)

Question 1

What did Ripke et al (2014) suggest?

Answer 1

• schizophrenia might be polygenic

- a number of candidate genes might be responsible for the illness

Question 2

What study did Ripke et al (2014) conduct and what was found?

Answer 2

• investigated candidate genes
• meta-analysis of studies
• 37,000 patients, 11,000 control
• 108 separate genetic variations = increased risk
• high levels of dopamine

Question 3

Evaluate Ripke et al (2014).

Answer 3

(+) High level of research support. Evidence is robust and hard to ignore as a cause for sz

(+) supported by dopamine hypothesis - D1/D2 receptors cause sz.

(-) other approaches need to be considered - behavioural develops sz

(-) diathesis stress model - more likely to get sz if gene is present but environmental factor triggers it

(-) mutation in parental DNA that causes offspring to get sz. Positive correlation between age of father and risk of sz. age <25, 0.7%. age >50 , 2%

Question 4

What study did Gottesman and Shields conduct?

Answer 4

• investigated 224 sets of twins (106 monozygotic, 118 dizygotic)
• 120M, 104F
• avg age 46 years, range of ethnic backgrounds
• conducted in London hospital
• longitudinal study over 25 years (1948 - 1993)
• one twin already had sz, measured concordance rates - likelihood of healthy twin developing sz
• in-depth interview, case notes, DSM used to diagnose sz

Question 5

What were the results from Gottesman and Shields’ study?

Answer 5

• 48% of MZ twins were concordant for sz at the end of the study
• 17% of DZ twins were concordant for sz at the end of the study
• sz has a genetic basis to some extent, esp MZ
• genetics less prominent of a cause for DZ

Question 6

Evaluate Gottesman and Shields.

Answer 6

(+) it was longitudinal, so development could be monitored

(+) results show concordance rates that support the biological argument

(+) both valid and reliable. Uses qualitative methods for diagnosis. 3 methods mean inter-rater reliability and high validity

(-) ignores behavioural approach. twins copy and model behavioural.

(-) relies on interviews - sz have difficulty with speech and communication. Negative effect on diagnosis and classification.

Question 7

What study did Kety et al (1994) conduct?

Answer 7

The Copenhagen High-Risk Study:

• prospective longitudinal study in 1972 (follow-up study 1974 - 1989)
• 207 adopted children, biological mothers had sz (high-risk)
• matched control group of 104 adopted children, healthy biological mothers (low-risk)
• ages of 10-18 at start of the study, matched in terms of age, gender, parental social-economic status

Question 8

What were the results from Kety et al (1994)?

Answer 8

• strong genetic basis for mental disorders
• 16.2% high risk, 1.9% low risk diagnosed with sz
• 18.8% high risk, 5% low risk diagnosed with schizotypal personality disorder
• overall: 35% high, 6.9% low for mental disorders

Question 9

Evaluate Kety et al (1994).

Answer 9

(+) ‘New York High-Risk Project’, longitudinal study for 25 yrs. Found similar results to Kety.

(+) Prospective study looks before symptoms develop. Doesn’t rely on self-reports (retrospective) - unreliable

(+) Fair, controlled, valid bc eliminates confounding variables - matched pairs

(-) cannot separate genes from environment. Children share environment with sz mother. Needs to be considered when interpreting results

(-) Mothers were diagnosed without DSM - may not have sz. Reliability of diagnosis is problematic