Can you inherit schizophrenia and bipolar disorder?

Professor Robin Murray: There are some genetic diseases where you get the gene, you get the illness.

There are no genes like this in psychiatry. It’s probably the case that there are, there may be hundreds of tiny genes that all combine together to increase your risk just in the same way that height, or weight, or intelligence are influenced by genes, but not by a single big gene, by lots of little genes which act together.

Is there a genetic predisposition to psychosis rather than a particular illness?

Professor Robin Murray: We used to think that schizophrenia was an entirely separate disease from bipolar illness, but now we know that that is not entirely the case, and this explains why sometimes when people see psychiatrists on one occasion, they might get a diagnosis of schizophrenia, and then they might on another occasion get a diagnosis of bipolar illness, or they might even on a third occasion get a diagnosis of schizoaffective disorder, which is somewhere in the middle. And the reason for this is not that psychiatrists are hopeless at diagnosis, but rather that these conditions are part of a continuum.

So you can inherit the same genes, and depending on what happens to you in your life, you can present with a picture that looks like schizophrenia, or present with a picture that looks like bipolar disorder.

You inherit a liability, a predisposition, in the same way as some families transmit a greater likelihood of developing diabetes, or asthma, or heart disease. So it’s not that you get a gene that causes these illnesses. What you do is you get a greater or a lesser risk. So if, for example, you have some predisposition, then environmental things might happen to you, which might increase your risk.

We think that, at least amongst people who develop severe schizophrenia, there is an increased risk of having had some developmental problem in the development of the brain. So that, anything that impairs the development of one’s brain, such as being born prematurely or being very hypoxic – starved of oxygen at birth – or having childhood meningitis, all of these things may cause a very subtle impairment of the development of the brain, and so this probably complicates the predisposition to psychosis, so if you have what we call these neuro-developmental risk factors, you are more likely to present with a picture that looks like schizophrenia.

So people who develop schizophrenia, people who have schizophrenia, often have difficult, complicated, thought disorder or some very subtle cognitive difficulties, not, by no means all, but it’s more frequent amongst people with schizophrenia. Interestingly, on the other hand, people who develop bipolar disorder often did terribly well as children, children who develop bipolar disorder, interestingly do better at school than the general population.

There is some interest that there may be some relationship between creativity and great ability and bipolar disorder.

It may be that having just a touch of bipolar genes or some minor predisposition gives you enthusiasm and creativity, it’s just if you get too many of the genes, the genetic loading, you then become ill.