Objective:

To examine associations between adolescents’ caffeine consumption, sleep duration, cortical structure, and later mental health problems.

Approach:

• Participants and measures: Researchers analyzed data from 9,632 adolescents aged 9–11 in the Adolescent Brain Cognitive Development Study. Caffeine intake was self-reported; sleep duration was reported by parents; brain structure was assessed by MRI.
• Analysis: Adjusted models examined caffeine associations with cortical thickness and surface area, and whether sleep and brain structure statistically mediated associations with mental health problems at 6 and 18 months.

Key Findings:

• Higher total caffeine intake was associated with lower total cortical surface area (standardized coefficient −0.03), but not average cortical thickness. Associations were reported at intake levels as low as one cup per week.
• Caffeinated soft drinks accounted for much of the surface-area association. Coffee and espresso intake was associated with slightly lower average cortical thickness (coefficient −0.02); tea intake was not significantly associated with cortical measures.
• Shorter sleep duration partially mediated associations between total caffeine intake or soft drink consumption and lower cortical surface area.
• At 6 months, small indirect associations linked caffeine intake or soft drink consumption with greater mental health problems through shorter sleep and lower cortical surface area. At 18 months, these associations persisted for total surface area, but not indi…

Interpretation:

The authors reported that shorter sleep and differences in cortical structure may form a pathway linking caffeine consumption with subsequent mental health problems. The observational findings do not establish causation, and sleep explained only part of the associations.

Limitations:

• The observational design and cross-sectional measurement of caffeine, sleep, and brain structure prevent causal or directional conclusions.
• Caffeine and sleep were reported by participants or parents, and beverage measures did not account for caffeine or sugar content.
• Caffeine intake was highly skewed; residual confounding by diet, health behaviors, stress, and adversity is possible.
• The US-based sample may limit generalizability.

Conclusion:

The authors called for further longitudinal and experimental research to clarify whether caffeine contributes directly to brain-development changes and to distinguish caffeine effects from sugar and other lifestyle factors.

Sources:

• Biological Psychiatry: Cognitive Neuroscience and Neuroimaging