Simple skin test gains traction as suicide marker

By Eleanor McDermid, Senior medwireNews Reporter

A large study of psychiatric inpatients supports the notion that electrodermal hyporeactivity may be an accurate marker of suicide risk.

Researchers Lars-Håkan Thorell (Linköping University, Sweden) and colleagues note that healthcare providers are largely successful in preventing suicide where a high risk has been identified.

“Thus, a good assessment procedure for suicide risk, to which the test of electrodermal hyporeactivity is expected to contribute, seems to be a key to the success of future suicide prevention,” they write in the Journal of Psychiatric Research.

The team defined electrodermal hyporeactivity as the loss of reactivity to a stimulus within the first five stimuli administered (ie, rapid habituation). It was most common among the 126 patients with bipolar disorder, affecting 80.2%, compared with 67.3% of 539 patients with unipolar depression, and 58.5% of 118 patients with other diagnoses (predominantly dysthymia).

“This is consistent with observations that patients with bipolar disorder carry the highest risk of suicide among affective disorders,” say Thorell et al. “However, it does not imply that such a high prevalence is typical for persons with bipolar disorder in general, since the sample comprises patients that were hospitalized, in part because of suicide risk.”

Of note, the presence of electrodermal hyporeactivity was not related to the severity of patients’ depression; it affected around two-thirds of patients in all categories according to the Beck Depression Inventory.

In all, 4.6% of patients later committed suicide, and 23.9% attempted to either before or after electrodermal testing. The sensitivities of electrodermal hyporeactivity for suicide were 75.0%, 81.5%, and 100% for patients with bipolar disorder, unipolar depression, and other diagnoses, respectively.

The corresponding specificities were “extraordinary high,” at 96.0%, 97.2%, and 100%, which the team says “indicates that a negative test result, i.e. being electrodermally reactive, may be a strong indication of very low risk of suicide.”

However, they caution that more prospective studies are needed to confirm its predictive value.

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