We know that young children with Asperger’s syndrome are prone to develop mood disorders (Attwood 2003a), and some children seem to be almost constantly anxious, which might indicate a Generalized Anxiety Disorder (GAD). One of the problems faced by children with Asperger’s syndrome who use their intellect rather than intuition to succeed in some social situations is that they may be in an almost constant state of alertness and anxiety, leading to a risk of mental and physical exhaustion. The child may have developed compensatory mechanisms to avoid anxiety-provoking situations such as school, by refusing to go to school or being mute at school (Kopp and Gillberg 1997). There may be intense anxiety or a phobic reaction to certain social situations, or to sensory experiences such as a dog barking, or to a change in expectations such as an alteration to the daily school routine. A referral to a clinical psychologist, psychiatrist or mental health service for children with a mood disorder may lead to a diagnosis of Asperger’s syndrome when a detailed and comprehensive developmental history is completed (Towbin et al. 2005).
Some children with Asperger’s syndrome can become clinically depressed as a reaction to their realization of having considerable difficulties with social integration. The depressive reaction can be internalized, leading to self-criticism and even thoughts of suicide; or externalized, resulting in criticism of others and an expression of frustration or anger, especially when the child has difficulty understanding a social situation. Blame is directed at oneself: ‘I am stupid’; or others: ‘It’s your fault.’ The signs of a clinical depression or problems with anger management could be the first indicators of a developmental disorder such as Asperger’s syndrome.

(Tony Atwood "The Complete Guide to Asperger's Syndrome")