The prevalence of suicidal ideation in bipolar disorder (BD) mainly depends on its definition and the type of measure used for its identification, with the Scale for Suicide Ideation (SSI) the most accurate measure, suggest study results.

“Different measures for ideation have the potential to cause inconsistency when correlates of suicidal ideation are investigated,” explain Erkki Isometsä (Helsinki University Central Hospital, Finland) and colleagues in the Journal of Affective Disorders.

To investigate how different definitions and measures for suicidal ideation influence its prevalence, correlates, and predictive validity in BD, the researchers measured suicidal ideation using different scales at baseline and at 6 months follow-up in 191 patients with BD who took part in the Jorvi Bipolar Study.

Measures included either having considered suicide, a Beck Depression Inventory (BDI) item 9 1 or 9 2, a Hamilton Depression Rating Scale (HAM-D) item 3 2 or 3 3, or a SSI sum score 6.

During the follow-up period, 15% of patients attempted suicide.

In total, 74% of patients were classified as presenting suicidal ideation by at least one of the measures. However, only 29% of these patients met the criteria for suicidal ideation under all definitions and agreement between definitions ranged from low to moderate, with the best agreement seen between SSI 6 and HAM-D item 3 2.

Furthermore, using a different cut-off as a threshold for ideation in BDI item 9 significantly affected the number of patients identified as having suicidal ideation, at 64% versus 9% when it was set at 1 versus 2, respectively.

BDI item 9 2 had the best positive predictive value for a suicide attempt during the next 6 months, but its sensitivity was quite low, at 33%.

The researchers determined that of the alternative definitions investigated, an SSI score of 8 provided an optimal combination of sensitivity (0.82) and specificity (0.69) for attempting suicide within the next few months.

Isometsä and team further found that the single common independent risk factor for suicidal ideation was the severity of depression and hopelessness.

They conclude: “The difference between the estimated prevalence of suicidal ideation based on different definition of suicidal ideation may be explained by different aspects and intensity of suicidal thoughts explored by these measurements.

“We recommend use of SSI for future studies evaluating suicidal ideation.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2009

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