Comparing the DSM-5 construct of Disruptive Mood Dysregulation Disorder and ICD-10 Mixed Disorder of Emotion and Conduct in the UK Longitudinal Assessment of Manic Symptoms (UK-LAMS) Study

It is important to understand new diagnostic entities in classifications of psychopathology such as the Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) (code F34.8) construct of Disruptive Mood Dysregulation Disorder (DMDD) and to compare it with possible equivalent disorders in other classificatory systems such as the International Classification of Diseases-10 (ICD-10), which has a category that superficially appears similar, that is, Mixed Disorder of Emotion and Conduct (MDEC) (code F92). In this study, the United Kingdom (UK) arm (UK-LAMS) of the US National Institute of Mental Health (NIMH) supported Longitudinal Assessment of Manic Symptoms (LAMS) multi-site study was used to evaluate and retrospectively construct DMDD and MDEC diagnoses in order to compare them and understand the conditions they co-occur with, in order to improve the clinical understanding. In particular, the phenomenology of UK-LAMS participants (n = 117) was used to determine whether DMDD is a unique entity within the DSM-5. The findings showed that 24 of 68 participants with either DMDD or MDEC (35.3%) fulfilled both diagnostic criteria for DMDD and MDEC, suggesting that these entities do contain overlapping features, particularly symptoms relating to Oppositional Defiant Disorder (ODD)/Conduct Disorder (CD), Attention Deficit Hyperactivity Disorder (ADHD)/Hyperkinetic Disorder (HKD) and/or an anxiety disorder. The data also showed that most of the participants who met DMDD criteria also fulfilled the diagnostic criteria for ODD/CD, ADHD, followed by an anxiety disorder. In this context, this raises the issue whether DMDD is a unique construct or whether the symptomology for DMDD can be better explained as a specifier for ODD/CD and ADHD. Unlike DMDD, MDEC clearly specifies that the label should only be used if emotional and conduct disorders co-exist.