Caffeine is a psychoactive stimulant drug that can have both positive and negative effects on different aspects of memory, and in some cases have no discernible impact at all. For many, it seems like caffeine only leads to positive effects on short-term and long-term memory if it is consumed daily in moderate doses, and preferably at around the same time every day. Much more research is needed before we can draw any firm conclusions.

The most pronounced positive effect of caffeine on memory appears to be found in groups comprised of test subjects aged 26-64 years. Caffeine consumption generally aids cognitive performance for this age group, as long at the intake doesn’t exceed 300 mg per day.

Caffeine and short-term memory

The scientific literature is conflicted when it comes to studies on caffeine and its impact on short-term memory. In some studies, caffeine have been shown to impair short-term memory. In others, caffeine enhanced the test subject’s short-term memory.

In an Auditory-Verbal Learning Test study published in 19861, subjects were asked to recall lists of words. The subjects that had received caffeine recalled fewer words than control subjects. Notably, subjects on caffeine showed a greater deficit in recalling the middle and end parts of the list.

Caffeine and long-term memory

Studies have shown caffeine to improve, impair and have no impact on long-term memory.

One study2 from 2007 showed that four weeks of caffeine consumption significantly reduced hippocampal neurogenesis compared to controls during the experiment. This could mean that caffeine is capable of inhibiting hippocampus-dependent learning and memory. It should be noted that this study was carried out on mice, not on humans.

A study3 on human test subjects instead showed improved long-term memory performance in test subjects with moderate to high habitual caffeine intake (mean 710 mg per week). In this study, a substance’s impact on cognitive processes was observed by asking the test subjects perform numerous cognitive tasks, including recalling words. For individuals with moderate to high habitual caffeine intake, more words were successfully recalled than for subjects in the low habitual caffeine intake group (mean 178 mg per week).

An improved delayed recall capacity linked to caffeine intake was also noticed in a similar study4 published in 1995. After a period of time with increased caffeine intake, test subjects were able to recall more words.

Time of day

In a study5, three groups of test subjects were compared at 01:00, 07:00, 13:00 and 19:00 o’clock. The three groups were the low caffeine intake group, the medium intake group and the high intake group. In this study, test subjects in the low intake group decreased their short-term memory performance later in the day, compared to the moderate-intake and the high-intake group.

The young and the old: Caffeine, memory and age

Age: 15-25 years

Studies carried out on test subjects in the age group 15-25 years have yielded interesting but also highly conflicting results. This might at least partly be due to this age group containing so many test subjects that aren’t regular consumers of caffeine.

If we look at adolescents and young adults without differentiating between habitual users and non-habitual users, caffeine seems to decrease short-term memory (including working memory) in this age group, while simultaneously increasing long-term memory. For young habitual consumers of caffeine however, there is an increase in both short-term and long-term memory.

In a large study6 published in 2004, regular caffeine intake was shown to be fairly beneficial to to young subjects.

Age: 65+

In the elderly, memory is usually at its best in the morning and will then gradually decline over the day.

In one study, elderly test subjects that consumed caffeine in the morning showed increased short-term and long-term memory in comparison to those who consumed placebo. The increase was especially noticeable in the late afternoon.

Another study7 showed that test subjects aged 65+ who regularly consumed caffeine in the morning were more alert and functioned on a higher level not just in the morning but throughout the day.

Males, Females & Caffeine

Several studies have indicated that caffeine might have a different effect on males vs females when it comes to both short-term and long-term memory. Exactly why that would be remains unknown. Caffeine’s impact on memory might be effected by oestrogen levels in the body.

Here area a few examples of interesting finds. If you want to dig deeper into a specific study, just take a look in the footnote, it will contain all the information you need to find the actual study.

Study 1: Caffeine impaired females, but not males, in a word-list test of short-term memory.8

Study 2: Females were tested within the first 5 days of their menstrual cycle and the study found that caffeine improved their performance on a short-term memory test.9

Study 3: No difference in the effect of caffeine on males vs females was found when long-term memory was tested.10