Understanding the mechanistic links between neurodevelopmental traits and internalising problems: the mediating roles...

Autism and attention deficit hyperactivity disorder (ADHD) are common neurodevelopmental conditions that have both consistently been linked to internalising problems like anxiety and depression. However, the mechanisms that underpin these associations are unclear, especially in adults. To fill this research gap, we used a trait approach to investigate two theoretically relevant dispositional characteristics that may explain these relationships: intolerance of uncertainty (IU) and negative problem orientation (NPO).

We recruited a large (N = 504), nationally representative sample of adults from the United Kingdom using Prolific. Participants provided basic demographic information and completed self-report measures of ADHD traits, autistic traits, internalising (depression and anxiety) symptoms, IU and NPO. Using parallel mediation analyses, we examined the roles of IU and NPO in the associations of ADHD and autistic traits with internalising symptoms.

We found that, together, IU and NPO fully mediated the association between autistic traits and internalising symptoms whilst accounting for participants' ADHD traits, age, sex and education level (standardised indirect effects: IU = 0.100, NPO = 0.139). Interestingly, these two dispositional characteristics only partially mediated the link between ADHD traits and internalising symptoms (standardised indirect effects: IU = 0.049, NPO = 0.128), suggesting that additional factors not captured by the mediation model may contribute to this positive relationship.

We conclude that a person's perception of their capacity to tolerate uncertain or ambiguous situations and their views on their (in)ability to effectively solve problems in their day-to-day lives may underpin the strong association between autism and internalising problems and, to a lesser extent, between ADHD and internalising problems.