Mental illnesses are complex, and are extremely variable in their presentation. In a woman, depression often comes out as tearfulness. In a man, the same depression might cause uncontrollable anger. To aid in the diagnosis of mental illness, physicians and mental health professionals rely on patterns, or rules-of-thumb, to aid their clinical skills. People tend to fall into patterns, or groups, though this isn’t always the case. The following describes four common subgroups of OCD, but rest assured these descriptions will not perfectly capture everyone suffering from the illness.