Compulsive behavior in the context of "Conscientiousness"

A habit (or wont, as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously.

A 1903 paper in the American Journal of Psychology defined a "habit, from the standpoint of psychology, [as] a more or less fixed way of thinking, willing, or feeling acquired through previous repetition of a mental experience." Habitual behavior often goes unnoticed by persons exhibiting it, because a person does not need to engage in self-analysis when undertaking routine tasks. Habits are sometimes compulsory. A 2002 daily experience study by habit researcher Wendy Wood and her colleagues found that approximately 43% of daily behaviors are performed out of habit. New behaviours can become automatic through the process of habit formation. Old habits are hard to break and new habits are hard to form because the behavioural patterns that humans repeat become imprinted in neural pathways, but it is possible to form new habits through repetition.

Substance dependence, also known as drug dependence, is a biopsychological situation whereby an individual's functionality is dependent on the necessitated re-consumption of a psychoactive substance because of an adaptive state that has developed within the individual from psychoactive substance consumption that results in the experience of withdrawal and that necessitates the re-consumption of the drug. A drug addiction, a distinct concept from substance dependence, is defined as compulsive, out-of-control drug use, despite negative consequences. An addictive drug is a drug which is both rewarding and reinforcing. ΔFosB, a gene transcription factor, is now known to be a critical component and common factor in the development of virtually all forms of behavioral and drug addictions, but not dependence.

The International Classification of Diseases classifies substance dependence as a mental and behavioural disorder. In the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) (released in 2013), substance abuse and substance dependence were eliminated and replaced with the single diagnosis of substance use disorders. This was done because "the tolerance and withdrawal that previously defined dependence are actually very normal responses to prescribed medications that affect the central nervous system and do not necessarily indicate the presence of an addiction."

Addiction is a neuropsychological disorder characterized by a persistent and intense urge to use a drug or engage in a behavior that produces natural reward, despite substantial harm and other negative consequences. Repetitive drug use can alter brain function in synapses similar to natural rewards like food or falling in love in ways that perpetuate craving and weakens self-control for people with pre-existing vulnerabilities. This phenomenon – drugs reshaping brain function – has led to an understanding of addiction as a brain disorder with a complex variety of psychosocial as well as neurobiological factors that are implicated in the development of addiction. While mice given cocaine showed the compulsive and involuntary nature of addiction, for humans this is more complex, related to behavior or personality traits.

Classic signs of addiction include compulsive engagement in rewarding stimuli, preoccupation with substances or behavior, and continued use despite negative consequences. Habits and patterns associated with addiction are typically characterized by immediate gratification (short-term reward), coupled with delayed deleterious effects (long-term costs).

Existential crises are inner conflicts characterized by the impression that life lacks meaning and by confusion about one's personal identity. They are accompanied by anxiety and stress, often to such a degree that they disturb one's normal functioning in everyday life and lead to depression. Their negative attitude towards meaning reflects characteristics of the philosophical movement of existentialism. The components of existential crises can be divided into emotional, cognitive, and behavioral aspects. Emotional components refer to the feelings, such as emotional pain, despair, helplessness, guilt, anxiety, or loneliness. Cognitive components encompass the problem of meaninglessness, the loss of personal values or spiritual faith, and thinking about death. Behavioral components include addictions, and anti-social and compulsive behavior.

Existential crises may occur at different stages in life: the teenage crisis, the quarter-life crisis, the mid-life crisis, and the later-life crisis. Earlier crises tend to be forward-looking: the individual is anxious and confused about which path in life to follow regarding education, career, personal identity, and social relationships. Later crises tend to be backward-looking. Often triggered by the impression that one is past one's peak in life, they are usually characterized by guilt, regret, and a fear of death. If an earlier existential crisis was properly resolved, it is easier for the individual to resolve or avoid later crises. Not everyone experiences existential crises in their life.

Dermatophagia (from Ancient Greek δέρμα (derma) 'skin' and φαγεία (phageia) 'eating') or dermatodaxia (from δήξις (dexis) 'biting') is a compulsion disorder of gnawing or biting one's own skin, most commonly at the fingers. This action can either be conscious or unconscious and it is considered to be a type of pica. Those affected with dermatophagia typically bite the skin around the nails, leading to bleeding and discoloration over time. Some people also bite on their skin on their finger knuckles which can lead to pain and bleeding just by moving their fingers.

In herpetology, dermatophagia is used to correctly describe the act in which amphibians and reptiles eat the skin they shed, but this is not what occurs in humans. Those diagnosed with this disorder do not develop wounds on the bitten areas of their hands or lose any skin. Instead, they experience a thickening of the skin being repeatedly bitten. Contemporary research suggests a link between impulse-control disorders and obsessive–compulsive disorders, and this was addressed in the DSM-5 when dermatophagia and other related disorders were classified as 'other specified obsessive-compulsive related disorders' and are given the specification of body focused repetitive behavior.

Obsessive–compulsive disorder (OCD) is a mental disorder in which an individual has intrusive thoughts (an obsession) and feels the need to perform certain behaviors (compulsions) repeatedly to relieve the distress caused by the obsession, to the extent where it impairs general function.

Obsessions are persistent unwanted thoughts, mental images, or urges that generate feelings of anxiety, disgust, or discomfort. Some common obsessions include fear of contamination, obsession with symmetry, the fear of acting blasphemously, sexual obsessions, and the fear of possibly harming others or themselves. Compulsions are repetitive actions performed in response to obsessions to reduce anxiety, such as washing, checking, counting, reassurance seeking, and situational avoidance.

Nicotine dependence is a state of substance dependence on nicotine. It is a chronic, relapsing disease characterized by a compulsive craving to use the drug despite social consequences, loss of control over drug intake, and the emergence of withdrawal symptoms. Tolerance is another component of drug dependence. Nicotine dependence develops over time as an individual continues to use nicotine. While cigarettes are the most commonly used tobacco product, all forms of tobacco use—including smokeless tobacco and e-cigarette use—can cause dependence. Nicotine dependence is a serious public health problem because it leads to continued tobacco use and the associated negative health effects. Tobacco use is one of the leading preventable causes of death worldwide, causing more than 8 million deaths per year and killing half of its users who do not quit. Current smokers are estimated to die an average of 10 years earlier than non-smokers.

According to the World Health Organization, "Greater nicotine dependence has been shown to be associated with lower motivation to quit, difficulty in trying to quit, and failure to quit, as well as with smoking the first cigarette earlier in the day and smoking more cigarettes per day." The WHO estimates that there were 1.24 billion tobacco users globally in 2022, with the number projected to decline to 1.20 billion in 2025. Of the 34 million smokers in the United States in 2018, 74.6% smoked every day, indicating the potential for some level of nicotine dependence. There is an increased incidence of nicotine dependence in individuals with psychiatric disorders, such as anxiety disorders and substance use disorders.