This outstanding achievement of international collaboration shows unequivocally that all the common psychiatric disorders have a very significant genetic correlation with each other. In other words, they are deeply connected genetically with a large proportion of liability shared between psychiatric/behavioural disorders, such as schizophrenia, bipolar disorder and major depression. This raises the question of why they present so differently? By contrast, when it came to common neurological disorders, such as Alzheimer’s disease, Parkinson’s disease and multiple sclerosis, there was no correlation between them or the behavioural disorders. The only exception was migraine, which, surprisingly, was slightly correlated with psychiatric disorders even though it is classified as neurological.

Other interesting findings related to the genetic correlations with other quantitative traits such as educational achievement and neuroticism. Surprisingly, early life educational attainment was positively correlated with a number of psychiatric illnesses, which tend to occur early in life, while being negatively correlated with neurological disorders such as Alzheimer’s disease, which occurs late in life. My connection to this research is through the genetic analysis of the Australian Schizophrenia Research Bank cohort, which was part of the schizophrenia working group of the psychiatric genomics consortium data used in the current study

This study shows that psychiatric disorders, such as bipolar disorder, depression and schizophrenia, often share a genetic background, while they are not so much genetically associated to neurological disorders.