Nicotine
Tobacco use, and indeed a greater likelihood of addiction to cigarettes, is also elevated in individuals with ADHD by approximately double compared to controls [63]. This pattern persists irrespective of gender [64]. Smoking cessation failure is associated with a diagnosis of ADHD in childhood [65] and individuals with ADHD have an earlier onset of smoking, higher rates of use and greater difficulty with abstinence [66]. Adults with ADHD are also less likely as a group to be successful in quitting compared to the general population [67].
Both nicotine and traditional pharmacological medications for ADHD operate as a psycho-stimulant. This shared functionality is consistent with the hypothesis that nicotine is used as a type of self-medication in these patient groups [68, 69]. The temporary effects of nicotine have been documented to enhance memory, reduce anxiety and tension, and improve symptoms of impulsivity, alertness, concentration and attention in adults with ADHD. All of which are considered to play a reinforcing role in the relationship between ADHD and smoking [65]. These transient improvements are likely to be due to the way nicotine acts on the release of neurotransmitters especially dopamine, serotonin and acetylcholine [68, 70]. The argument of substance dependence by way of self-medication is, as previously mentioned, known as the “gateway hypothesis” [70]. Reducing the symptoms of ADHD using psychostimulant medication (e.g., methylphenidate) impacts on the dopamine transporter (DAT) and has been found to significantly delay the onset of smoking in young adults [71, 72]. The variety of noradrenergic and dopaminergic drugs such as bupropion and moclobemide are both nicotine effective and also beneficial in the treatment of ADHD [70, 73].
