Higher caffeine consumption may be associated with more severe depression symptoms, according to a new study. However, researchers also identified a paradoxical pattern in people suffering from insomnia or poor sleep quality, where caffeine appeared to temporarily mask depression symptoms and weaken the statistical association.
On Monday, local time, researchers at the University of Arizona College of Medicine presented findings at the American Psychiatric Association (APA) annual meeting, analyzing the effects of caffeine intake on depression, sleep, stress, and fatigue in 1,007 adults aged 22 to 60.
The researchers measured participants' levels of depression using the Patient Health Questionnaire-9 (PHQ-9) scale, while also assessing insomnia severity, daytime sleepiness, fatigue, and stress levels. Caffeine intake was classified based on the number of cups consumed per day, including coffee and energy drinks.
The analysis showed that higher daily caffeine intake tended to correspond with higher depression scores. In particular, the group consuming three or more cups per day had significantly higher depression scores than those who did not consume caffeine at all. Insomnia, fatigue, stress, and excessive daytime sleepiness were each independently associated with higher depression scores.
However, a reversal emerged in the insomnia patient group. Among those with moderate or severe insomnia, the group with the highest depression scores were those who did not consume any caffeine. Insomnia patients who drank at least one cup of caffeine per day showed a relatively moderate increase in depression scores tied to sleep disturbances. A similar trend was observed in the group with poor sleep quality.
The researchers and experts emphasized that this should not be interpreted as meaning "caffeine helps with depression." The study is a cross-sectional analysis of a specific point in time and cannot establish causation. This means it is not possible to determine whether caffeine worsened depression symptoms or whether depressed individuals sought out more caffeine.
"We wanted to examine how caffeine affects the relationship between sleep problems and depression symptoms from biological, psychological, and social perspectives," said lead researcher Mira Kaur Marwaha.
Professor Gregory Scott Brown of the APA, who was not involved in the study, said, "We have only just opened the door to a complex issue," pointing to limitations such as the failure to account for differences in coffee types, added sugar, and individual caffeine consumption habits. "Since caffeine is a substance that directly acts on the mind, clinicians need to carefully examine patients' consumption patterns in clinical settings," he said. "Because individual responses vary greatly, the findings from a single study should not be generalized."
