Trichotillomania (repeatedly pulling one’s hair) is a condition formerly found in the “impulse control disorder not elsewhere classified” section. The diagnostics in DSM-5 involve visible hair loss, a feeling of tension immediately prior to pulling, and a sense of relief or pleasure when pulling out hair. According to DSM-5, individuals have to repeatedly attempt to stop hair pulling. This requirement was not part of the diagnostic criteria in DSM-IV and brings the hair-pulling disorder more in line with the repetitive and ritualized behavior and urges in OCD (Ameringen et al. 2014).

Recent results confirm evidence for the genetic transmission of hair pulling and suggest a familial subtype of hair pulling with comorbid OCD. However, there was no evidence for an etiologic relationship between hair pulling and skin picking (Keuthen et al. 2014).

Rogers et al. (2014) propose a stepped care model with a Web-based self-help program as step 1 followed by the opportunity to engage in an in-person habit reversal training for 8 weeks (step 2). The model was tested in 60 patients and proved to be highly accepted. On top of that, participants showed significant reduction of symptoms and increased quality of life.

As for trichotillomania, excoriation disorder was previously classified under impulse control disorders. Even with a lifetime prevalence estimate of between 2 and 4 % (Grohol 2013), excoriation disorder is new to DSM-5. Patients with this disorder have to suffer from a recurrent urge to pick at one’s own skin resulting in skin lesions. The disorder is further characterized by repeated attempts to decrease or stop the skin picking. Excoriation disorder can be very time consuming as individuals sometimes spend up to 8 h per day picking their skin.

Unlike OCD, skin picking is not preceded by obsessions but a high level of tension and an urge to scratch, pick, or squeeze otherwise healthy skin. Several studies suggest that symptom severity tends to fluctuate with stress levels but typically has a chronic course associated with substantial emotional distress and functional impairments (e.g., Odlaug et al. 2010).

Recent data support the conceptualization of excoriation disorders as a valid diagnostic entity (Snorrason et al. 2013). First, skin picking is characterized by a distinct constellation of symptoms, phenomenology, and course. Second, recent data suggest an underlying dysfunction and familiarity that cannot be completely explained by comorbid disorders. Third, skin picking is associated with certain characteristic environmental and temperamental factors such as stress and emotional reactivity.

SSRIs seem to be less effective in the treatment of skin picking, in contrast to OCD, whereas the opioid agonist naltrexone, for example, has demonstrated efficacy in this disorder. Similarly, exposure treatment, the method of first choice in OCD, seems to be ineffective, whereas patients with skin picking, like patients with trichotillomania, benefit from habit reversal training (Grant et al. 2012). Here, patients are instructed to develop awareness of the picking behavior and, in a next step, to replace it with a harmless habit that makes it impossible.

Hoarding disorder is a chronic and very debilitating condition characterized by a difficulty in discarding and/or excessive acquiring of things, gathering of clutter, and subsequent distress and impairment due to the hoarding behavior. Often, functional impairment also extends to relatives who live with the patient, so involving family members in the treatment is crucially important.

There is mounting evidence that hoarding pathology is associated with worse treatment outcome compared to other OC symptoms (e.g., Knopp et al. 2013). A large body of research suggests that hoarding disorder is clinically and neurobiologically distinct from OCD and necessitates a somewhat different kind of treatment. In line with this, hoarders seem to have a different pattern of cerebral glucose metabolism than non-hoarding patients with OCD (Saxena et al. 2004).

Though OCD symptoms and hoarding symptoms occasionally co-occur, many patients with hoarding disorder do not suffer from OCD. Recent results, however, suggest that individuals with only hoarding disorder show similar deficits on measures of executive functions as patients with both OCD and severe hoarding. This points toward a similar underlying neuropsychological dysfunction. The authors interpret their results as an argument for the inclusion of hoarding disorder within the new Obsessive–Compulsive and Related Disorders chapter (Morein-Zamir et al. 2014).

DSM-5 moved body dysmorphic disorder (BDD) from the somatoform disorders to the obsessive–compulsive spectrum disorders. Recent research on BDD yields a prevalence rate of about 1.8 % (Buhlmann et al. 2010).

Patients with BDD are constantly haunted by feelings of ugliness or an imagined defect in their looks despite a normal appearance or only a slight and trivial abnormality in appearance. Physical features that commonly raise concerns about perceived imperfections or flaws involve the skin, nose, ears, mouth, genitals, or hair. Some subjects, for example, focus their concern on perceived excessive facial hair or a disfigured shape of the nose. The preoccupation must cause clinically significant distress or impaired social or occupational functioning, clearly differentiating the disorder from normal concerns about one’s appearance. Many subjects tend to constantly ask for reassurance from others, are engaged in ritualistic checking behaviors, and make time-consuming attempts to improve the perceived imperfection. Others show avoidance behavior, for example, social withdrawal and avoiding mirrors; alternating between excessive checking and avoidance is also not unusual.

Insight in BDD is generally poorer than in OCD. Phillips et al. (2006), for example, investigated the two variants of BDD, namely, delusional and non-delusional. Their study found that about one third (36 %) of BDD subjects were delusional. The proportion of delusional BDD was higher in adolescents than in adults. A recent comparison of insight in BDD and OCD revealed that in both disorders insight can range from excellent to absent. Most OCD patients, however, showed excellent or good insight on the Brown Assessment of Beliefs Scale (BABS), and only 2 % of OCD patients had delusional beliefs. In contrast, the majority of BDD patients scored within the range of poor or absent insight (Phillips et al. 2012), and 32 % showed delusional beliefs.

Buhlmann and Winter (2011) point to several similarities between OCD and BDD. These include checking rituals, similar age of onset and course of illness as well as tendencies to hide the disorder from others due to excessive shame or embarrassment, and a high comorbidity. Major depression and anxiety disorders, however, are also very often comorbid with BDD, and the disorder is frequently associated with suicidal ideation (31 %) and suicide attempts (22 %) (Buhlmann et al. 2010).

So far, serotonin reuptake inhibitors and cognitive behavioral treatment are considered the treatment of choice. A recently evaluated manualized modular cognitive behavioral therapy for BDD over 24 weeks was well received by patients and proved very effective in reducing BDD symptoms (Wilhelm et al. 2014).

Substance-/medication-induced OCRD must occur immediately after or during substance intoxication or withdrawal or develop as a consequence of a specific medication. For example, obsessions or compulsive rituals can be caused by certain stimulating drugs containing amphetamines or by corticosteroid therapy (Bhangle et al. 2013).

As OCD can also be caused by certain medical conditions, a medical evaluation is always required to rule out that a medical factor is causing obsessions or compulsions. Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS), for example, can lead to a sudden onset of severe OCD symptoms in children. There is evidence that patients with this type of OCD may benefit from antibiotics in addition to CBT or medication with antidepressants (Murphy et al. 2012). Another example is certain neurodegenerative diseases of the basal ganglia such as Huntington’s or Wilson’s disease, which can be associated with OC symptoms. New onset of OCD has also been reported secondary to other neurological disorders such as brain tumors, stroke lesions, postencephalopathic disorders, or traumatic brain injury.

Finally, there are other specified and unspecified obsessive–compulsive and related disorders for individuals who fulfill some but not all the diagnostic criteria for one of the disorders described above. One example is body dysmorphic-like disorder with actual flaws, which command excessive preoccupation. Another example is obsessional jealousy, which is characterized by non-delusional preoccupation with a partner’s perceived infidelity and repetitive behaviors or mental acts concerning the perceived infidelity. Also Jikoshu-kyofu or olfactory reference syndrome – a strong fear of having bad body odor – falls into this category.