Schizophrenia and bipolar disorder have for decades been regarded as two distinct psychotic disorders when it comes to definitions and risk factors.
Schizophrenia is a psychotic illness that causes delusions and hallucinations - bipolar disorder also known as manic depression, causes extreme mood swings from deep depression to manic episodes.
But now a study by Swedish researchers has found the two most common psychotic disorders have the same genetic causes and questions the current separate classification of the diseases.
Though schizophrenia and bipolar disorder have always been treated as quite distinct in many ways some experts have had doubts about such strict classification and this doubt has been bolstered by modern genetic technology which has revealed that certain genes appear to affect both disorders.
To unravel the puzzle the Swedish scientists analysed the records of two million families, including 35,985 patients with schizophrenia, 40,487 patients with bipolar disorder, and the blood relatives of both to better understand whether schizophrenia and bipolar disorder have the same genetic causes.
The study covered a 30 year period from 1973 to 2004 and it was found that members of families where either schizophrenia or bipolar disorder was present had the same genetic factors which increased their risk of developing the same condition - the culprit in this risk is the genetic factors and only slightly due to shared environmental factors.