Methods. The 135 participants in the Canadian program of genetic testing to predict the risk of Huntington's disease were followed prospectively in three groups according to their test results: the increased-risk group (37 participants), the decreased-risk group (58 participants), and the group with no change in risk (the no-change group) (40 participants). All the participants received counseling before and after testing. Standard measures of psychological distress (the General Severity Index of the Symptom Check List 90-R), depression (the Beck Depression Inventory), and well-being (the General Well-Being Scale) were administered before genetic testing and again at intervals of 7 to 10 days, 6 months, and 12 months after the participants received their test results.

Results. At each follow-up assessment, the decreased-risk group had lower scores for distress than before testing (P<0.001). The increased-risk group showed no significant change from base line on any follow-up measure, but over the year of study there were small linear declines (P<0.023) for distress and depression. The no-change group had scores lower than at base line on the index of general well-being at each follow-up (P less-than-or-equal-to 0.045). At the 12-month follow-up, both the increased-risk group and the decreased-risk group had lower scores for depression and higher scores for well-being than the no-change group (P less-than-or-equal-to 0.049).

Conclusions. Predictive testing for Huntington's disease has potential benefits for the psychological health of persons who receive results that indicate either an increase or a decrease in the risk of inheriting the gene for the disease.