Multiple Morbidities in an Inner-City English Substance Misuse Treatment Service: Hierarchical Cluster Analysis to Derive Treatment Segments.

Comorbid needs of people attending substance use treatment has been well documented although there is an assumption of heterogeneity in the treated population. This study utilized hierarchical cluster analysis to explore the extent and nature of client segments within the treated population. A retrospective review of comorbid health and social needs of a random sample of client case-notes ( = 300) was undertaken on all people known to treatment in an urban, inner-London community out-patient treatment service during 2018-2019. A hierarchical cluster analysis using Ward's linkage method was implemented to explore the data to determine and describe emergent clusters. Inter cluster differences were investigated further by modeling methods. High rates of physical health (63%) and mental health (50%) need were noted across the entire treatment population. The hierarchical clustering identified three discrete segments of the treatment population. The largest segment (46% of clients) was complex, socially impacted chaotic heroin and crack misusers exhibiting a wide range of multiple morbidities including social needs such as housing, unemployment and offending. This cluster also were more likely to report acute needs such as Emergency Department attendance, utilization of ambulatory services and will and episodic disengagement disengage episodically from treatment. A second segment (24% of clients) exhibited similar drug using profiles to the largest cluster, although with fewer comorbid issues. This cluster tended to be older and more likely to report respiratory conditions. A third cluster (25% of clients) was more likely to be alcohol misusers who were new to treatment. Treated populations are likely to be relatively heterogeneous across a range of social harms, physical and mental health needs. Identifying multidimensional needs of segments within treatment services allows for the creation of tailored treatment interventions.