Increased sensitivity to positive social stimuli in monozygotic twins at risk of bipolar vs. unipolar disorder

J Affect Disord. 2018 May;232:212-218. doi: 10.1016/j.jad.2018.02.055. Epub 2018 Feb 21.


Background: Abnormalities in affective cognition are putative endophenotypes for bipolar and unipolar disorders but it is unclear whether some abnormalities are disorder-specific. We therefore investigated affective cognition in monozygotic twins at familial risk of bipolar disorder relative to those at risk of unipolar disorder and to low-risk twins.

Methods: Seventy monozygotic twins with a co-twin history of bipolar disorder (n = 11), of unipolar disorder (n = 38) or without co-twin history of affective disorder (n = 21) were included. Variables of interest were recognition of and vigilance to emotional faces, emotional reactivity and -regulation in social scenarios and non-affective cognition.

Results: Twins at familial risk of bipolar disorder showed increased recognition of low to moderate intensity of happy facial expressions relative to both unipolar disorder high-risk twins and low-risk twins. Bipolar disorder high-risk twins also displayed supraliminal attentional avoidance of happy faces compared with unipolar disorder high-risk twins and greater emotional reactivity in positive and neutral social scenarios and less reactivity in negative social scenarios than low-risk twins. In contrast with our hypothesis, there was no negative bias in unipolar disorder high-risk twins. There were no differences between the groups in demographic characteristics or non-affective cognition.

Limitations: The modest sample size limited the statistical power of the study.

Conclusions: Increased sensitivity and reactivity to positive social stimuli may be a neurocognitive endophenotype that is specific for bipolar disorder. If replicated in larger samples, this 'positive endophenotype' could potentially aid future diagnostic differentiation between unipolar and bipolar disorder.

Keywords: Affective cognition; Bipolar disorder; Emotion reactivity; Emotion regulation; Endophenotype; Twin study.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Twin Study

MeSH terms

  • Adult
  • Affective Symptoms / genetics
  • Affective Symptoms / physiopathology*
  • Attention
  • Bipolar Disorder / genetics
  • Bipolar Disorder / physiopathology*
  • Cognition
  • Depressive Disorder / genetics
  • Depressive Disorder / physiopathology*
  • Diseases in Twins / genetics
  • Diseases in Twins / physiopathology*
  • Emotions / physiology
  • Endophenotypes*
  • Facial Expression
  • Female
  • Humans
  • Male
  • Risk
  • Twins, Monozygotic / genetics*