Studies have shown that caffeine can enhance brain function in a shorter period of time, and this prevents adenosine from binding to its receptors. ChronicHowever, chronic caffeine intake may up-regulate adenosine receptors and exacerbate adenosine levels and some adenosine actions in the brain.

The results from observationobservational studies on the relationship between coffee intake and risk of depression, and the relationship between caffeine consumption and depression remain controversial.
We conducted a meta-analysis with a dose-response analysis to quantitatively summarize the evidence about the association between coffee and caffeine intakesintake, and risk of depression.

For dose-response analysis, evidence of a linear association was found between coffee consumption and depression, and the risk of depression decreased by 8% (relative risk = 0.92, 95% confidence interval = [0.87, 0.97], p = 0.002) for each cup/day increment in coffee intake; a nonlinear association was found between caffeine consumption and depression, the risk of depression decreased faster and the association became significant when the caffeine consumption was above 68 mg/day and below 509 mg/day.

There are a lot of studies that suggest caffeine addiction may affect our ability to sleep well, and therefore we are in a vicious cycle of lack of sleep and addictionan activated addiction to the effect of caffeine activated.
The quality of sleep is altered by caffeine with effects dependent on the timing of consumption, the amount consumed, and individual differences in sensitivity; thus. Thus, assessment of consumption is necessary in any patient presenting with insomnia.