Differentiating Schizophrenia From Bipolar Disorder Can Be Difficult

Although schizophrenia and bipolar disorder have long been considered distinct illnesses, the demarcation between the two may be thinner than previously believed.

So reported some psychiatrists at the annual meeting of the Canadian Psychiatric Association in St. John's, Newfoundland, in August.

The psychiatrists were Glenda MacQueen, M.D., Ph.D., chair of psychiatry at the University of Calgary; Roger McIntyre, M.D., an associate professor of psychiatry and pharmacology at the University of Toronto, and Ashok Malla, M.D., a professor of psychiatry at McGill University.

There are a number of reasons why the line between schizophrenia and bipolar disorder seems to be fuzzier than previously thought, the speakers indicated.

Some of the same brain abnormalities that can be found in subjects with schizophrenia can also be found in bipolar subjects, McIntyre reported. Moreover, these same brain abnormalities can be found in some unaffected first-degree relatives of individuals with schizophrenia and in some unaffected first-degree relatives of individuals with bipolar disorder, suggesting that they are inherited and common to people with either schizophrenia or bipolar disorder.

Even though psychiatrists usually assume that cognitive impairment is only experienced by individuals with schizophrenia, not by those with bipolar disorder, individuals with the latter can experience it as well, MacQueen said.

And just as bipolar individuals can have cognitive deficits, they can also experience another hallmark of schizophrenia—psychotic symptoms, MacQueen stated.

Still another link between schizophrenia and bipolar disorder is the risk of the metabolic syndrome—weight gain, metabolic disturbances, even cardiovascular disease. Certainly the reason why patients with either schizophrenia or bipolar disorder develop the syndrome can sometimes be blamed on the use of psychotropic medications or on the pursuit of unhealthy lifestyles, Malla said. But in other instances, he suspects, the metabolic syndrome can be attributed to biological abnormalities common to both schizophrenia and bipolar disorder. One possible candidate is a gene that codes for inflammatory responses in the body, he noted. It was recently identified in both bipolar and schizophrenia subjects.

Another commonality between schizophrenia and bipolar disorder is the difficulty that patients with either disorder have in achieving a functional recovery, the speakers pointed out. True, more bipolar patients than schizophrenia patients do recover, but nonetheless not all bipolar patients do, they said.

Finally, could it be that some patients who start off with bipolar disorder evolve into having schizophrenia? The speakers believed that this is a possibility.

Thus, as the case for an overlap between schizophrenia and bipolar illness grows, it raises questions about diagnosis. When should patients receive a diagnosis of schizophrenia? When should they receive a diagnosis of bipolar disorder? And how does a diagnosis of schizoaffective disorder fit into the picture? There are no simple answers here, the speakers noted.

Some audience members concurred. For instance, one reported that she has had great trouble determining whether mentally ill people in a homeless shelter have schizophrenia, bipolar disorder, or schizoaffective disorder, especially when they also abuse alcohol or use cocaine. ▪