Gottesman (1991)

Aimed to examine how vulnerable the children of two parents with mental illness are to developing a mental illness themselves.

A cohort study - involves looking at a group of a population

Natural experiment - comparing two or more naturally occuring groups

IV (Naturally Occuring)  = Parental schizophrenia or bipolar disorder

DV = If the offspring receive a diagnosis of any mental illness

Participants drawn  from the Danish population (approcimately 2.7 million) of people born before 1997, who had an identifiable mother and father

Data sampled in 2007 , therfore the minimum age of participants was 10

Anyone diagnosed with schizophrenia, bipolar or unipolar were identified from the Psychiatric Register

Couples who had both been admitted to a psychiatric hospital were identified for the study (secondary data)

196 couples - both had a disgnosis of schizophrenia, and their 270 children

83 couples -both had a diagnosis of bipolar disorder, and their 146 children

A control group of people with only one parent being admitted was also studied

A control group of people with neither parent admitted was studied

A control group of the 'general public' (no data on whether they had had parents with psychiatric illnesses or not)

Researchers used data from National Statistics to identify people with a diagnosis

The children of the couples, aged from 10 years old up to 52 years old , were checked on the same register for any diagnosis of mental disorders

Used the classifications from ICD-8 and ICD-10

For both schizophrenia and bipolar disorder the risk of mental illness was much greater for offspring of two parents with a disgnostic:

27.3% of having a diagnosis of schizophrenia by age 52

39.2% for schizophrenia and related conditions

67.5% developed a mental illness of some sort

For offspring with one parent diagnosed with schizophrenia the risk was:

7% with a diagnosis of schizophrenia

11.9% for any diagnosis

For those with neither parent having any diagnosis, the risk was:

1.2% for schizophrenia

14.1% for any mental illness

Bipolar:

24.95% of offspring with two bipolar parents developed the disprder by age 52

36% developed either bipolar disorder or depression

44.2% developed a mental illness of some sort

Of those with one bipolar parent:

4.4% developed bipolar disorder themselves

9.2% a mental illness

If both parents had a diagnosis of a mental illness, there was a high risk of their offspring also being diagnosed with a mentla illness

The risk of offspring being admitted to hospital with a diagnosis of schizophrenia is higher if both parents have been admitted with the same diagnosis

The risk of offspring being admitted to hospital with a diagnosis of  either bipolar or unipolar depressive disorder is higher if both parents have been admitted with the same diagnosis

There is evidence to support the genetic explanation of mental illness