Professor David Lewis discusses the differences between schizophrenia and bipolar disorder, noting that there here may be some shared risk factors.
Two illnesses that occur commonly are schizophrenia and bipolar disorder. One of the major advances that was made, now a century ago by Kraepelin, was to discriminate these two disorders based upon certain of their features, but also their life course. For many individuals, when they first present with symptoms, what we call the cross-sectional appearance or the appearance of the symptoms at a given point in time, can be quite similar between schizophrenia and bipolar illness. It’s only as we follow individuals over time do we begin to see the different courses of the illness and can make the discrimination between the two. Now, on the other hand, genetic studies now are showing that for a least certain genes, risk is increased for both schizophrenia and bipolar disorder. So there may be some shared risk factors for those two illnesses, which may perhaps account for why, clinically, there are certain similarities between the illnesses.