Asperger syndrome can be misdiagnosed as a number of other conditions, leading to medications that are unnecessary or even worsen behavior; the condition may be at the root of treatment-resistant mental illness in adults. Diagnostic confusion burdens individuals and families and may cause them to seek unhelpful therapies. Conditions that must be considered in a differential diagnosis include other pervasive developmental disorders (autism, PDD-NOS, childhood disintegrative disorder, Rett disorder), schizophrenia spectrum disorders (schizophrenia, schizotypal disorder, schizoid personality disorder), attention-deficit hyperactivity disorder, obsessive compulsive disorder, depression, semantic pragmatic disorder, multiple complex developmental disorder and nonverbal learning disorder (NLD).[3]