Depression in people with a learning disability might occur more frequently than often assumed with many people still running the risk of being underdiagnosed, according to new research.

The study published in Journal of Mental Health Research in Intellectual Disabilities found that the choice of instrument for measuring depression in individuals with a learning disability is critical.

Researchers found that the symptoms of depression are undoubtedly present in this group and probably even to a much higher degree than in the general population. It is also clear that, if not specifically tested for, these symptoms might still go unnoticed.

Estimates of the prevalence of depression in people with a learning disability range from almost nonexistent to 39%. This study aimed to measure the outcomes of three screening instruments to find out more about the prevalence in people with mild or borderline disability.

It found that using the standard cutoff values, the numbers of people identified as depressed by the tests were 31%, 44%, and 22%, respectively. These were high numbers, and they did not refer to the same cases. When scoring above cutoff on all three tests simultaneously was the criterion, 13.7% of the participants were identified as depressed.

Multiple tests for depression needed in learning disability groups

There was some evidence that people living under supervision had more symptoms of depression than those living independently, which the authors say could correspond with the notion that people in the former category experience more personal problems and limitations in daily life, which may have been the reason for their not being able to live independently in the first place.

The authors recommend the use of multiple tests that rely on different sources of information. "Such a combination of tests should preferably include a self-report questionnaire and an informant-based questionnaire," they said.

"If one wants a sensitive procedure, one could consider people scoring above cutoff on either test as being potentially depressed. If one wants to minimize the risk of identifying a person as depressed who in reality is not, one could rely on the combined results, meaning that only those who score above cutoff on all tests are referred for further evaluation."

They added that a lot of additional research into the validity of existing test procedures will probably be needed to attain this goal, research in which expert clinical judgment as a criterion will still prove to be essential.