Does monotropism bridge ADHD and ASD? A latent profile analysis in adults

Introduction
The clinical presentation of attention-deficit/hyperactivity disorder (ADHD) and autism spectrum disorder (ASD) in adults is heterogeneous, with symptom overlap, masking behaviors, and developmental continuity complicating diagnostic differentiation. Despite increasing recognition of ADHD and ASD co-occurrence, research in adult populations remains limited, and few studies examine both conditions simultaneously while accounting for underlying attentional mechanisms. The aim of this study was to examine adult neurodevelopmental heterogeneity through the joint assessment of ADHD symptoms, autistic traits, and monotropism using latent profile analysis (LPA).

Material and methods
The study included 101 adults who completed the DIVA-5, RAADS-R, and the Monotropism Questionnaire as part of a comprehensive diagnostic process. Participants underwent a series of diagnostic sessions conducted by trained clinicians, during which standardized questionnaires constituted one component of a multimethod assessment. Latent profile analysis was applied to identify subgroups characterized by distinct configurations of neurodevelopmental traits.

Results
Latent profile analysis identified three profiles: 1) an ADHD-dominant profile characterized by elevated inattention in both childhood and adulthood and low levels of autistic traits; 2) a mixed ADHD–ASD profile characterized by high inattention, increased impulsivity in adulthood, and elevated communication difficulties and circumscribed interests; and 3) a low-symptom profile. Although monotropism did not statistically differentiate the profiles, its highest levels were observed in the mixed profile.

Conclusions
The findings highlight the relevance of person-centered, multidimensional assessment approaches in adult neurodevelopmental evaluation. They also support further research on monotropism as a transdiagnostic attentional dimension in clinical assessment.