An evaluation of functional mental capacity in forensic mental health practice: the Dundrum capacity ladders validation study

Background: Because of the potential gravity of finding a person incompetent, assessment of mental capacity is challenging for clinicians. We aimed to test validity of a new structured professional judgement tool designed to assess functional mental capacity in three domains - finances, welfare and healthcare. Methods: Fifty-five male forensic psychiatric patients with Schizophrenia were interviewed using the Dundrum Capacity Ladders - a new semi-structured interview, and scores were assigned on a stratified scoring system, measuring ability to understand, reason, appreciate the personal importance of the decision at hand and communicate a decision. Data were also gathered pertaining to level of therapeutic security at the time of interview, diagnosis, neurocognitive function and a validated measure of real world function. Results: The results show that internal consistency and inter-rater reliability were high for all items. There were correlations between higher scores of functional mental capacity, neurocognitive function and measures of real world function in this population. Correlations were in the range 0.358 to 0.693, effect sizes that were moderate to high. Conclusions: The DUNDRUM Capacity Ladders appear to be a valid measure of functional mental capacity in this population. Further prospective studies of functional mental capacity as a measure of recovery are now required.