I've had a number of cases where they present with depression due to their difficulties with social functioning. Some struggle to live independently; in a couple of cases I've had to basically make the diagnosis in middle-aged individuals who were still living with frail elderly parents, and went into complete tailspins when dad passed away, or mom went into a nursing home. Can be a tough situation. For younger adults I am aware of some community resources for adult PDD, social skills training, etc. Look diligently and you may find them where you are. But it can definitely be an area where people fall through the cracks.