problems in pooling patients together, said William Potter of Merck Research Laboratories, co-chair of the workshop. He stressed that quality control, standardized measures, and training are essential for pooling studies. Age group is also a crucial issue. Studies in adults may be inapplicable to children and adolescents, who often manifest or express symptoms of a psychiatric disorder in ways that diverge from adults. Thus, diagnosis itself may be problematic.

Common definitions of suicidality are essential in clinical practice and in defining outcome measures in clinical trials, Potter commented. Referring simply to “suicidality” can become complicated because different researchers may exclude various behaviors in the definition. The FDA uses C-CASA (the Columbia Classification Algorithm for Suicide Assessment) terms to define “suicidality” as attempt or completion as well as thinking about suicide (suicidal ideation), or preparatory acts toward imminent suicidal behavior if intent is to die (Posner et al., 2007). Others exclude ideation, thereby defining suicidality more restrictively as an attempt, preparatory acts toward imminent suicidal behavior, or completion.

The following definition was used for the purpose of the workshop for consistency (Box I-1). One practical reason for excluding suicidal ideation in the definition of suicidality was that one of the key goals of the workshop was to determine whether suicidal ideation has predictive power as a surrogate measure for suicidality. When a speaker uses a different definition of suicidality, it is noted in the text.

BOX I-1

Definition of Terms Used During Workshop

Suicidal ideation refers to thoughts of suicide.


Suicidality, for the purpose of this workshop, refers to completed suicide, suicide attempt, or preparatory acts toward imminent suicidal behavior.



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