It has also been shown that depression and polysubstance dependence are often both present at the same time. If a person is genetically predisposed to be depressed then they are at a higher risk of having polysubstance dependence.Possibly the most widely accepted cause of addictions is the self-medication hypothesis, that views substance addiction as a form of coping with stress through negative reinforcement, by temporarily alleviating awareness of or concerns over the stressor. People who use substances learn that the effects of each type of substance works to relieve or better painful states. They use substances as a form of self-medication to deal with difficulties of self-esteem, relationships, and self-care. Individuals with substance use disorders often are overwhelmed with emotions and painful situations and turn to substances as a coping method. Sociocultural
The sociocultural causes are areas in a persons life that might have influenced their decision to start and continue using multiple substances. Sociocultural causes can be divided into social causes and cultural causes. Social Causes: Some studies have shown that adolescents have one of the highest rates of polysubstance dependence. According to one study this population, ages 12–25, represents about half of the nations population that uses illicit substances. Of these individuals, half of them have started using substances by the end of 12th grade. This could be attributed to social expectations of peers, peer pressure to fit it, or a way of numbing their emotions.
Sub-gingival calculus formation and chemical dissolution
Sub-gingival calculus is composed almost entirely of two components: fossilized anaerobic bacteria whose biological composition has been replaced by calcium phosphate salts, and calcium phosphate salts that have joined the fossilized bacteria in calculus formations. The initial attachment mechanism and the development of mature calculus formations are based on electrical charge. Unlike calcium phosphate, the primary component of teeth, calcium phosphate salts exist as electrically unstable ions. The following minerals are detectable in calculus by X-ray diffraction: brushite (CaHPO4 · 2 H2O), octacalcium phosphate (Ca8H2(PO4)6 · 5 H2O), magnesium-containing whitlockite (Ca9(Mg,Fe)(PO4)6(PO3OH)), and carbonate-containing hydroxyapatite (approximately Ca5(PO4)3OH but containing some carbonate).The reason fossilized bacteria are initially attracted to one part of the subgingival tooth surface over another is not fully understood; once the first layer is attached, ionized calculus components are naturally attracted to the same places due to electrical charge. The fossilized bacteria pile on top of one another, in a rather haphazard manner. All the while, free-floating ionic components fill in the gaps left by the fossilized bacteria. The resultant hardened structure can be compared to concrete; with the fossilized bacteria playing the role of aggregate, and the smaller calcium phosphate salts being the cement. The once purely electrical association of fossilized bacteria then becomes mechanical, with the introduction of free-floating calcium phosphate salts. The "hardened" calculus formations are at the heart of periodontal disease and treatment.