Drug addiction may be a goal-directed choice driven by excessive drug value in negative
affective states, a habit driven by strong stimulus-response associations, or a compulsion
driven by insensitivity to costs imposed on drug seeking. Laboratory animal and human
evidence for these three theories is evaluated. Excessive goal theory ...
Drug addiction may be a goal-directed choice driven by excessive drug value in negative
affective states, a habit driven by strong stimulus-response associations, or a compulsion
driven by insensitivity to costs imposed on drug seeking. Laboratory animal and human
evidence for these three theories is evaluated. Excessive goal theory is supported by
dependence severity being associated with greater drug choice/economic demand. Drug
choice is demonstrably goal-directed (driven by the expected value of the drug) and can be
augmented by stress/negative mood induction and withdrawal – effects amplified in those
with psychiatric symptoms and drug use coping motives. Furthermore, psychiatric
symptoms confer risk of dependence, and coping motives mediate this risk. Habit theory of
addiction has weaker support. Habitual behaviour seen in drug exposed animals often does
not occur in complex decision scenarios, or where responding is rewarded, so habit is
unlikely to explain most human addictive behaviour where these conditions apply.
Furthermore, most human studies have not found greater propensity to habitual behaviour
in drug users or as a function of dependence severity, and the minority that have can be
explained by task disengagement producing impaired explicit contingency knowledge.
Compulsion theory of addiction also has weak support. The persistence of punished drug
seeking in animals is better explained by greater drug value (evinced by the association with
economic demand) than by insensitivity to costs. Furthermore, human studies have
provided weak evidence that propensity discount cost imposed on drug seeking is
associated with dependence severity. These data suggest that human addiction is primarily
driven by excessive goal-directed drug choice under negative affect, and less by habit or
compulsion. Addiction is pathological because negative states powerfully increase expected
drug value acutely outweighing abstinence goals.