18 yr old boy compusive liar we need to help him

Please provide more information.

What are some examples of his compulsive lies? Does he live at home? Is he in school? Are there drugs/alcohol involved? Are there siblings? Is there violence surrounding his behavior?

How long have things been this way, and what have you tried so far.

If you are his parent and he is done with high school, give him 30 days to move out, and mean it. Evict him.

When someone uses 'help cope' in the same breath as 'compulsive liar,' it reeks of manipulation on the 18 year old's part, and wishy washy guilty enabling on the parent's part.