W
hy does bipolar disorder persist at a constant level across generations and around the world if it can be associated with depression, psychosis, despair and even suicide? Are there bipolar benefits associated with the same genes that can lead to the disorder?
In August 2014, in the American Journal of Psychiatry, a very careful and detailed research study identified a large group of identical twins discordant for bipolar disorder (meaning, one of the twins had the diagnosis, and the other did not).
Since they were identical twins, their genes were the same, and in this study, their families were the same as well (this was not a study of identical twins separated at birth).
Unaffected twins had higher “positivity” scores (scores of optimism and positive orientation towards the future) than the control group (twins without bipolar). The affected twins (those who developed bipolar) did not have the same increased level of positivity (possibly due to the negative effects on outlook of having the disorder, being hospitalized, etcetera).
Unaffected twins of bipolar individuals had more social ease, confidence, and assertiveness.
The members of the bipolar twins without the disorder also had greater verbal learning and fluency than the control group, and than their affected twin member.
They learned information faster and were better at expressing themselves than controls and than their twin members.
The authors conclude –
To our knowledge, this is the first systematic study to indicate a possible familial compensatory advantage to bipolar illness in discordant twin pairs. These findings contribute to mounting evidence linking creativity and enhanced cognitive functioning and risk for bipolar disorder (9–13, 20, 22) and may inform models of mechanisms underpinning this association. That liability for bipolar disorder may confer temperament and neurocognitive benefits could provide one explanation for the genetic persistence of this illness.
“Enhanced Neurocognitive Functioning and Positive Temperament in Twins Discordant for Bipolar Disorder” Am J Psychiatry Higier et al.; AiA:1–8