Chunk #10 — 3. Results — 3.2 Association of Suicide with Current Smoking — 3.2.1. Possible Mechanisms — 3.2.1.2. Smoking as a Psychological or Physical Toxin
There are plausible mechanisms to account for such behavioral toxicity. Reductions in serotonin have been repeatedly linked to increased hostility, aggression, and importantly, to increased suicide (Kamali et al. 2001). Chronic nicotine exposure reliably reduces serotonin and its metabolites in animals (Olausson et al. 2002). Several studies have examined whether this also occurs in humans. In a postmortem study, smokers had lower levels of serotonin and its metabolites in various brain regions than did nonsmokers (Benwell et al. 1990). Smokers had lower levels of serotonin metabolites in the cerebrospinal fluid (Malone et al. 2003) but not in platelets (Pivac et al. 2004; Schmidt et al. 1997). Smokers also had lower levels of prolactin in response to a serotonin inhibitor (Berggren et al. 2003; Malone et al. 2003; Anthenelli & Maxwell 2000) – an indicator of lower serotonergic function; however, smoking could have influenced prolactin levels by nonserotonergic mechanisms (Anthenelli & Maxwell 2000). Unfortunately, except for the postmortem studies, the above studies were performed only in smokers vs nonsmokers with current alcohol dependence. Also, in these studies, it was unclear whether
