A multi-trajectory analysis of commonly co-occurring mental health issues across childhood and adolescence

Objective: Developmental trajectories of specific mental health issues vary considerably across individuals and this variation can often be summarised in terms of a small number of clinically meaningful subtypes. Given the high levels of heterotypic and homotypic comorbidity in mental health that have been previously identified, we evaluated whether it was also possible to summarise the joint developmental trajectories of multiple commonly co-occurring mental health issues in this way. Method: We evaluated the combined developmental trajectories of attention deficit hyperactivity (ADHD), internalising and externalising symptoms in a normative sample of youth with data at ages 7,8,9,10,11,12,13 and 15 using group-based multi-trajectory modelling. Multinomial logistic regression was used to evaluate predictors of group membership. Results: Our optimal model included six trajectory groups, labelled ‘unaffected’, ‘normative maturing’, ‘internalising’, ‘multimorbid late onset’, ‘multimorbid remitting’, and ‘multimorbid with remitting externalising’. Examining covariates of group membership suggested that males and bully victims tend to have complex mental health profiles; academic achievement and smoking during pregnancy have general associations with mental health irrespective of symptom developmental trajectories or combination; and maternal post-natal depression is primarily related to symptoms that are already in evidence by childhood. Conclusion: Developmental trajectories of commonly co-occurring mental health issues can be usefully summarised in terms of a small number of developmental subtypes. These subtypes more often than not involve multiple co-occurring mental health issues. Their association with mental health covariates depends on the combination of and developmental timing of symptoms in ways that suggest they can be clinically informative.