No recent review and very little empirical research has looked directly at the specific risk factors for the combination of the two problems. This was potentially one of the most interesting areas covered in this review, but there was a lack of longitudinal data in the field. Very few studies have addressed pathways through the full range of provision, most take a small section only. Given the complexity, it was difficult to assess whether or not the system works. This is also a critical area for some systematic research, looking both at how people got into the wrong place and how they could be helped to move on.
Further attention needs to be given to the issue of outcomes.
Effectiveness research Two key questions were identified. The first, of whether intervention or provision is effectively targeted and delivered, has not been answered. There is more research on the second, concerning which specific interventions work with MDOs. Treatment of psychopathy and management of personality disorder have received particular attention. There is a central problem that interventions are most likely to be successful if they are based on a clearly articulated theory, but theory development in the whole area of MDOs is lagging a considerable way behind.