I can only really speak for myself on this. And, on my own, I'm not a representative sample.
I have Asperger's Syndrome (an ASD), and I've had clinical depression and anxiety during adulthood. Things got so bad at one point that I was admitted to a mental health unit as an in-patient. I was also unable to complete a degree due to these mental health problems.
But I don't think it was the ASD itself that directly caused such mental illness. I've only much more recently had my ASD diagnosed, and I'm pretty sure the mental health problems were largely due to the consequences of my undiagnosed ASD not being taken into account and accommodated. Hopefully, the diagnosis I've now got will help avoid or reduce such problems in the future.
My lad got very low at primary (to the point of School refusal.) my other lad had a meltdown more at Secondary and College level.
I think a large amount depends on the level of support a child receives for their needs and how they feel they are coping with what life throws at them.
Is their something specific that you think is affacting your childs depression?
Not sure how common it is in children but it is certainly recognised in adults. As I understand it this commonly arises from difficulties with getting the world to understand one's point of view. If you repeatedly hit a brick wall in dealing with the world, because you find it difficult to understand the world and it fails to understand you, then you eventually get ground down and feel that everything is hopeless. These are components of depression.
I now recognise that, pre-diagnosis, I was verging on being clinically depressed. Now, post-diagnosis and having read around the subject a lot (in a rather circumscribed interest sort of way ;-) ) I can see how differences in thought style etc can lead to great misunderstandings between the ASD sufferer and the NT world. With this understanding I can tackle my communication issues and hopefully not hit so many brick walls.
I hope this makes sense? :-) I think it is likely to apply to children - they are not a different species after all.
Stress is another issue for ASD sufferers but that is another topic.
