| Tobacco smoke–medication interactions | Tobacco smoke, but not nicotine, induces the metabolism of several psychotropic medications through the CYP1A2 enzyme. Medication doses for some psychotropic medications will need to be reduced if the patient achieves abstinence from smoking. |
| Nicotine withdrawal | Symptoms of nicotine withdrawal, such as irritability, sleep problems, fatigue, impaired concentration, and appetite changes, may mimic symptoms of psychiatric illness. Nicotine withdrawal can be alleviated with nicotine replacement therapy or with varenicline to some extent. |
| Persistence | Successful smoking cessation requires persistent efforts since most patients require more than one attempt to quit. Every attempt to quit provides opportunities for learning how to quit, and patients are more likely to succeed with each subsequent try. |
| Caffeine–tobacco smoke interaction | Tobacco smoke also induces the metabolism of caffeine. Smoking cessation without a reduction in caffeine intake may lead to symptoms of caffeine toxicity, including anxiety, restlessness, sleep problems, and irritability, which can mimic symptoms of psychiatric illness. |