Caffeinated drinks—such as coffee, tea, soda, and energy drinks—pep you up temporarily, but they may have a more insidious effect. They may worsen depression, insomnia, and anxiety.
Caffeine and depression.
Several studies have looked at caffeine intake and depression. For example, one study found that, among healthy college students, moderate and high coffee drinkers scored higher on a depression scale than did low users. Interestingly, the moderate and high coffee drinkers also tended to have significantly lower academic performance. There is a reason for this effect and it relates to the chronic effects of caffeine on the brain.
Other studies have implicated that depressed patients tend to consume fairly high amounts of caffeine (e.g., greater than 700 mg/day, or about 7 cups of coffee). In addition, caffeine intake has been positively correlated with the severity of symptoms in psychiatric patients, especially related to panic disorders and depression.
Caffeine affects cortisol levels (the stress hormone). In one study, researchers gave healthy men and women different doses of caffeine throughout the day and found that the caffeine spiked their cortisol levels1.
Caffeine and sugar can be a bad combo.
The combination of caffeine and refined sugar seems to be even worse than either substance consumed alone. Several studies have found a strong association between this combination and depression. In one study2 published in Behavior Therapy, 21 women and 2 men responded to an advertisement requesting volunteers “who feel depressed and don’t know why, often feel tired even though they sleep a lot, are very moody, and generally seem to feel bad most of the time.”
After baseline psychological testing, the subjects were placed on a caffeine- and sugar-free diet for one week. The subjects who reported substantial improvement were then given either a capsule containing caffeine and a Kool-Aid drink sweetened with sugar, or a placebo capsule containing cellulose and a Kool-Aid drink sweetened with an artificial sweetener, for up to six days.
About 50% of the test subjects became depressed during the period where they were getting caffeine and sucrose. The reason? Researchers believe it's because caffeine worsens blood sugar control and when combined with sugar, causes blood sugar volatility that really stresses out the brain.
Caffeine may impact sleep.
I'd advise anyone who is prone to depression, insomnia, anxiety, or any psychological disorder to avoid caffeine as much as possible. If you can cut sugar out of your diet too, even better.
Michael T. Murray, N.D., is a naturopathic physician regarded as one of the world's top authorities on natural medicine. An educator, lecturer, researcher, and health food industry consultant, he is the author of more than 30 books, including his newest book The Complete Book of Juicing, Revised and Updated (Clarkson Potter, January 2014). Readers who sign up for Weekly Natural Facts Newsletter at the website (drmurray.com) will receive a free copy of Dr. Murray's new ebook, Stress, Anxiety and Insomnia! What the Drug Companies Won't Tell You and Your Doctor Doesn't Know.