Nonverbal interpersonal attunement and extravert personality predict outcome of light treatment in seasonal affective disorder.

We investigated whether personality and nonverbal interpersonal processes can predict the subsequent response to light treatment in seasonal affective disorder (SAD) patients. In 60 SAD patients, Neuroticism and Extraversion were assessed prior to light treatment (4 days with 30 min of 10.000 lux). From videotaped clinical interviews, the nonverbal interpersonal attunement (i.e. equalizing durations and frequencies of elements of behaviour between conversation partners) was registered for the patients' support seeking and the interviewers' support giving behaviour. The higher Extraversion and the more the patients and the interviewers got attuned over the interview, the more favourable the outcome of light treatment was. Hence, personality and nonverbal interpersonal processes may be involved in the response to light treatment in SAD.