When it comes to diagnoses and treatment for mental health disorders, all US-based doctors and American insurance companies turn to the same source of information: "The Diagnostic and Statistical Manual of Mental Disorders," or DSM. The American Psychiatric Association notes that the DSM handbook is the authoritative guide for the diagnosis of mental health disorders that clinicians depend on to match patients with known conditions and recommended interventions.

Of all the mental health disorders defined therein, including depression, bipolar disorder, PTSD and eating disorders, there's one that physicians are asked about especially often: obsessive-compulsive disorder, or OCD. Interestingly, many of the people asking about it, "have symptoms of OCD, but do not meet the full criteria for a diagnosis according to the DSM," says Juanita Guerra, PhD, a clinical psychologist practicing meditation in New Rochelle, New York.

That distinction is important because OCD-related symptoms are far more common than the disorder itself. "Clinically diagnosed OCD affects only about 2.5 million adults in the U.S.," says Amanda Darnley, PsyD, a practicing psychologist based in Philadelphia. 

What triggers OCD?

Those individuals struggling with OCD experience intrusive thoughts or irrational fears that lead them to specific behaviors. Severity of the disorder varies, but many people who have OCD experience a range of OCD symptoms that often include compulsory actions, a fear of dirt or germs and an expectation that things have to be arranged or done in a specific way or bad things will happen to them or someone they love. 

While known causes aren't fully understood, genetics or hereditary factors are often thought to be related to OCD, "and it can also have a component of learned behavior such as watching someone with certain behaviors over time and learning those behaviors," says Jesse Bracamonte, DO, a family medicine physician at Mayo Clinic in Arizona. 

Is OCD a chemical imbalance?

Another theory is that OCD occurs as a result of biological changes in one's natural chemistry or brain function. Scientists suspect this involves an imbalance between chemical messengers or neurotransmitters in certain brain regions, per research from Cambridge University and University College London − though such research is still ongoing. 

Regardless of what causes the disorder, "a combination of several factors (related to OCD) all have to be present together in order to become a clinical mental illness," says Siggie Cohen, PhD, a child development specialist and popular parenting coach. She explains that some such factors are related to nature, "such as personality traits of inflexibility, rigidity, fearfulness and even organic levels of stress and anxiety that exceed what’s considered typical;" while other factors may be related to nurture, "such as a lack of proper understanding, support and early intervention."

When does OCD require professional help?

Though some people manage mild OCD symptoms or perceived OCD-related symptoms such as perfectionism on their own, clinically diagnosed OCD as outlined in the DSM usually requires professional help or medical interventions. Darnley says such help may come in the form of talk or behavioral therapy or certain medications. 

Cohen says a professional can also help anyone who has OCD understand what contributes to or triggers their compulsive behaviors to show how the disorder may be limiting them, "so they can become open to accepting the tools that can help them manage it."

Guerra says that the disorder becomes a problem, "when the individual begins spending an excessive amount of time engaging in ritualistic behavior." She explains that not getting help when ritualistic behaviors turn obsessive often leads to secondary problems. "As with any anxiety disorder," she says, "when the symptoms of OCD begin to interfere with the individual’s overt functioning or their ability to work or socialize, it is time to seek professional help." 

OCD is not that uncommon:Understand the symptoms of obsessive compulsive disorder.