THERE was something odd about my new patient. She was elegantly dressed and self-possessed, and yet she was slowly, rhythmically chewing gum, something I rarely see in my psychiatry sessions. Was she trying to cover up anxiety about this first encounter, I wondered, or was she perhaps hoping to project a kind of cool, laid-back style?

We talked for a long time about why she had come to see me. Then, as is my practice with a new patient, I asked what, if any, psychiatric medications and nonprescription, psychoactive substances — legal or illegal — she had used. Her answer was a new one for me. She stated that she chewed approximately 40 pieces of nicotine gum per day and had done so for well over a decade.

Responses to this question are often illuminating and can be rather humbling. Although doctors are trained to focus on prescription medications, there are and have always been nonprescription “remedies” for psychiatric conditions. And people’s preferences for one type of substance over another can give a glimpse into their symptoms and even their brain chemistry.

If a patient tells me he falls asleep on cocaine, I wonder if he might have attention deficit disorder. A patient who smokes marijuana to calm down before important business meetings leads me in the direction of social phobia or other anxiety disorders. I often wonder if people who take ketamine recreationally might be depressed, since this anesthetic has been shown to have antidepressant effects and is, in fact, being investigated for potential therapeutic use.