People with congenital insensitivity to pain have reduced life expectancy.In The Greatest Show on Earth: The Evidence for Evolution, biologist Richard Dawkins addresses the question of why pain should have the quality of being painful. He describes the alternative as a mental raising of a "red flag". To argue why that red flag might be insufficient, Dawkins argues that drives must compete with one other within living beings. The most "fit" creature would be the one whose pains are well balanced. Those pains which mean certain death when ignored will become the most powerfully felt. The relative intensities of pain, then, may resemble the relative importance of that risk to our ancestors. This resemblance will not be perfect, however, because natural selection can be a poor designer. This may have maladaptive results such as supernormal stimuli.Pain, however, does not only wave a "red flag" within living beings but may also act as a warning sign and a call for help to other living beings. Especially in humans who readily helped each other in case of sickness or injury throughout their evolutionary history, pain might be shaped by natural selection to be a credible and convincing signal of need for relief, help, and care.Idiopathic pain (pain that persists after the trauma or pathology has healed, or that arises without any apparent cause) may be an exception to the idea that pain is helpful to survival, although some psychodynamic psychologists argue that such pain is psychogenic, enlisted as a protective distraction to keep dangerous emotions unconscious.
In the sense that it is associated with irresistible urges to perform unwanted repetitive behavior, trichotillomania is akin to some of these conditions, and rates of trichotillomania among relatives of OCD patients is higher than expected by chance. However, differences between the disorder and OCD have been noted, including: differing peak ages at onset, rates of comorbidity, gender differences, and neural dysfunction and cognitive profile. When it occurs in early childhood, it can be regarded as a distinct clinical entity.Because trichotillomania can be present in multiple age groups, it is helpful in terms of prognosis and treatment to approach three distinct subgroups by age: preschool age children, preadolescents to young adults, and adults.In preschool age children, trichotillomania is considered benign. For these children, hair-pulling is considered either a means of exploration or something done subconsciously, similar to nail-biting and thumb-sucking, and almost never continues into further ages.The most common age of onset of trichotillomania is between ages 9 and 13. In this age range, trichotillomania is usually chronic, and continues into adulthood. Trichiotillomania that begins in adulthood most commonly arises from underlying psychiatric causes.Trichotillomania is often not a focused act, but rather hair pulling occurs in a "trance-like" state; hence, trichotillomania is subdivided into "automatic" versus "focused" hair pulling. Children are more often in the automatic, or unconscious, subtype and may not consciously remember pulling their hair.