This is the third installment in our discussion on how problems in thinking may represent our major challenge in dealing with bipolar, rather than our moods. I was first tipped off to this in 2001 when I came across a lengthy review article in the journal Bipolar Disorders authored by Carrie Bearden, now at UCLA. Significantly, I ran into Dr Bearden in 2007 at a research conference on schizophrenia. Could there be an overlap between bipolar and schizophrenia? Hold that thought.

In 2004, I was literally hit over the head in the form of a presentation by Deborah Yurgelun-Todd of Harvard at the American Psychiatric Association meeting. There, I heard Dr Yurgelun-Todd make a strong case that cognitive deficits should be regarded as a core feature of bipolar disorder. This endorses the observations of the pioneering diagnostician Emil Kraepelin, who referred to “amentia” in his description of manic-depression in his classic 1921 text.

In her APA talk, Dr Yurgelun-Todd referred to a study where she and her colleagues scanned the brains of 11 stable bipolar patients while undergoing the Stroop Color Word-Task. The Stroop is one among a battery of tests that measures for “executive function.” Executive function refers to the brain’s capacity for problem solving, forward planning, allocation of attention. motivation, concept formation, self-regulation, and monitoring, and working memory

Thus, during the Stroop, if the word, "Blue," is printed in green, you are expected to call out "blue" rather than "green." Likewise with the next color-coded word in the sequence, and the next.

The Stroop is fairly simple, but you need to be on your cognitive game. Typically, individuals with schizophrenia fare a lot worse than the general population, but what about those of us with bipolar? Dr Yurgelin-Todd found significant delays in the ability to respond with correct answers compared to 10 healthy controls. Her study also found decreased activation of the brain region responsible for processing the task compared to the controls.

In real life, this translates to being an American tourist having to contend with crossing a street in London, with the traffic coming at you from the wrong direction. I heard this example two weeks ago at the NAMI CA conference in Sacramento. The speaker was Cameron Carter of UC Davis, a prominent schizophrenia researcher.

Just about all we know about cognitive dysfunction comes from schizophrenia research. Despite schizophrenia being classified by the DSM as a “psychotic” disorder, the clear consensus from the experts is that the brain’s breakdown in processing information is what truly defines this illness. This helps explain why only 10 percent of those with schizophrenia work full time.

But the full-time employment rates with bipolar are also depressingly abysmal - 35 percent, according to a STEP-BD survey.

Granted, schizophrenia is hardly the same illness as bipolar, but can we make a case for an overlap? Consider: Nearly all the candidate genes for schizophrenia are also suspect in bipolar, including dysbindin, neuregulin, COMT, DISC-1,and BDNF, among others. These genes regulate all manner of thinking activity, from how neurons talk to each other to the maintenance of healthy brain cell function.