Chunk #14 — 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
The fourth mechanism is that (a) the nicotine in smoking acts as an antidepressant, and (b) some lines of evidence indicate antidepressants can cause suicide. Nicotine, in low doses, appears to have anti-depressant effects. It reverses learned helplessness in animals (Semba et al. 1998), normalizes sleep patterns in never-smoking depressed patients (Haro & Drucker-Colin 2004), and can act as a partial antidepressant in depressed, never-smoking humans (McClernon et al. 2006). Other studies show a nicotine antagonist can act as an antidepressant (George et al. 2008). Although debatable, some lines of evidence suggest antidepressants increase suicide risk in adults (Mann et al. 2006; Licinio & Wong 2005; Reith & Edmonds 2007). The mechanisms by which antidepressants might increase suicide are unclear; e.g., antidepressants might induce akathesia, aggression, panic attacks, mania, or obsessions (Teicher et al. 1993). One mechanism that might be relevant is that antidepressants might cause chronic insomnia that would worsen mood. Smoking does appear to worsen sleep and, this does appear to be due to nicotine (Haro & Drucker-Colin 2004; Htoo et al. 2004). In addition, several studies have
