'Autism is the Arena and OCD is the Lion': Autistic adults' experiences of co-occurring obsessive-compulsive disorder and repetitive restricted behaviours and interests.

Repetitive behaviours and interests are a hallmark feature of autism. It is very common for autistic people to experience mental health difficulties, such as obsessive-compulsive disorder. Previous research has investigated similarities and differences between obsessive-compulsive disorder symptoms and repetitive behaviours in autism through questionnaires and observation studies. This is the first study to interview autistic adults about their personal experiences of differentiating between obsessive-compulsive disorder symptoms and repetitive behaviours related to autism. We interviewed 15 autistic adults who experience obsessive-compulsive disorder symptoms. We recorded these interviews and carefully analysed these to find themes. We found some differences between repetitive behaviours and obsessive-compulsive disorder. Participants said repetitive behaviours are part of who they are and what they want to be doing, whereas obsessive-compulsive disorder symptoms conflicted with how they view themselves. Obsessive-compulsive disorder was said to cause negative emotions, while participants said they experience lots of different emotions when doing repetitive behaviours. A similarity participants reported was trying to stop themselves from doing obsessive-compulsive disorder symptoms and repetitive behaviours that other people can see. There was also overlap between obsessive-compulsive disorder and repetitive behaviours. Participants talked about experiences when obsessive-compulsive disorder would take over routines and make them feel more intense and negative. Also, participants' special interests were sometimes connected to the obsessions they experienced. We conclude that clinicians can use these findings to support conversations with autistic clients in differentiating between repetitive behaviours and obsessive-compulsive disorder symptoms. We also think that further research investigating how obsessive-compulsive disorder symptoms might be hidden by autistic and typically developing people is needed.