Schizotypal personality disorder usually co-occurs with major depressive disorder, dysthymia, and generalized social phobia.[11] Furthermore, sometimes schizotypal personality disorder can co-occur with obsessive-compulsive disorder, and its presence appears to affect treatment outcome adversely.[12] The personality disorders that co-occur most often with schizotypal personality disorder are schizoid, paranoid, avoidant, and borderline.[13]