Of the 16 studies included, 11 stated that their case subjects were heroin-dependent; one stated that their case subjects were mainly (85%) dependent on morphine or smack (heroin), though some (15%) were addicted to pentazocine/buprenorphine;13 and the remaining four did not indicate to which specific opioid(s) their case subjects were addicted (Table 1). Most studies used either the Diagnostic and Statistical Manual 24-III-R14 or -IV15 criteria to diagnose opioid dependence. Exceptions to this were the studies by Bond and colleagues, which used federally-regulated criteria for admission to a methadone maintenance program;2 Crowley and colleagues which used medical records and urine screening;11 Drakenberg and colleagues, who used post-mortem opiate toxicology, history of opiate abuse, and the presence or absence of physical body-needle tracks;1 and Shi and colleagues who interviewed physicians.20 All but two studies excluded individuals with major psychiatric disorders (for example depression and schizophrenia) from their control groups.16,22 Li and colleagues excluded such patients, but these authors relied on subject’s self-reported medical history, rather than formal psychiatric evaluation, which may have failed to exclude control subjects who in fact had
