What does caffeine do to your memory and concentration in the long run?

Caffeine makes you sharper in the short term. When you are tired or less alert, it modestly but reliably improves your attention, reaction speed and decision-making. That effect is strongest when you are not at your best, for example after a poor night's sleep or in the middle of a draining afternoon.

For your long-term memory, caffeine probably makes little to no difference. An analysis involving more than 415,000 participants, which used genetic variants to filter out chance and lifestyle effects, found no causal effect of habitual coffee drinking on memory, reasoning or reaction time. That is a strong signal that caffeine does not structurally build up your memory.

Working memory, the part of your memory that lets you keep track of several things at once, responds inconsistently to caffeine. On simple tasks there is a small benefit. On tasks that place a genuinely heavy load on your working memory, caffeine can actually hinder performance. A consistently positive effect on working memory does not exist.

Dosage matters. At low to moderate amounts, caffeine is well tolerated and even has a mildly mood-enhancing effect. At higher doses, anxiety and nervousness increase, which in turn undermines concentration. Using caffeine late in the day is another risk: it disrupts sleep, and sleep is essential for consolidating what you have learned during the day.

With prolonged daily use, the body becomes accustomed to caffeine. The alertness you initially felt then begins to level off. If you stop suddenly, concentration can temporarily dip due to withdrawal. Whether caffeine protects against cognitive decline in old age remains unclear for now: studies contradict one another and the available evidence is too weak to draw a conclusion.