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Caf9.5
Caffeine Research
Probably helps
1,891 peer-reviewed studies
Showing the 983 most recent of 1891 studies.
All 1908 database studies by type: RCT 1554 · Meta-Analysis 194 · Systematic Review 96 · Review 58 · Observational 3 · Case Study 1 · Cohort 1 · Crossover 1
What the evidence says
Probably helps
Caffeine helped in about half (3/5) of the studies that measured an effect — promising, but not unanimous.
Most evidence is from high-quality meta-analyses and randomised trials published 2008–2026 with a typical study size of 75 participants.
Based on 980 studies · 154 meta-analyses · 686 RCTs · 146,688 total participants
Confidence
High confidence
What the studies found
3helped2unclear· 975 more without graded effect data
By outcome
Cognitive functionEnhances short-term memory consolidation and recall · 30-60 minutes
Weight managementAcute thermogenic and lipolytic effect · 30-60 minutes
Too few graded studies34 studies
Sleep & insomnia
Too few graded studies16 studies
Safety profile
Too few graded studies13 studies
Focus & attentionImproved attention, concentration, and reaction time · 30-60 minutes
Too few graded studies12 studies
Migraine & headache
Too few graded studies11 studies
By the numbers
Pulled from 92 studies with measurable effects
Likely real effects
67%
across studies
People studied
147k
typical study: 75 people
Strongest designs
840
154 pooled, 686 randomised
Showed benefit
60%
3/5 studies
How long studies ran
1–4 weeks
1
3+ months
1
Populations Studied
General population10
Athletes6
Adults3
Healthy participants2
Active research area
501 studies in the last 5 years · Latest meta-analysis: 2026
200820172026
1Meta-Analysis2026
In plain English: This is the first meta-analysis specifically focused on aerobic time-trial performance to suggest that pre-exercise ingestion of low caffeine doses (1.3-3 mg·kg-1) may enhance endurance performance by reducing time-trial completion time.
However, aerobic responses to caffeine vary substantially, with time-trial performance ranging from ~-3% to +16%.
Data were pooled using standardized mean differences (SMDs) and 95% confidence intervals under random-effects models, and risk of bias was assessed using the Cochrane Risk of Bias tool.
Both low and moderate caffeine doses significantly reduced time-trial completion time relative to placebo.
2IBD riskMeta-Analysisn=13,209 · very large study2026
In plain English: The relationship between caffeine intake and IBD risk varies by region, age, caffeine source, smoking, and education level.
Wu X et al. · Journal of gastroenterology and hepatology (2026)
No clear effect
← WorseNo effectBetter →
The meta-analysis showed no significant association between caffeine intake and IBD (RR = 0.84, 95% CI = 0.68-1.04).
In Americans, caffeine increased UC risk by 68% (RR = 1.68, 95% CI = 1.17-2.42).
Age analysis showed caffeine increased IBD risk by 4.52 times in those ≤18 (RR = 4.52, 95% CI = 1.59-12.88) but decreased risk by 7% in those >18 (RR = 0.93, 95% CI = 0.73-1.18).
3Cognitive performance and alertnessReviewCited 509×2016
In plain English: Following low (∼40mg or ∼0.5mgkg-1) to moderate (∼300mg or 4mgkg-1) caffeine doses, alertness, vigilance, attention, reaction time and attention improve, but less consistent effects are observed on memory and higher-order executive function, such as judgment and decision making.
McLellan TM et al. · Neuroscience & Biobehavioral Reviews (2016)
Alertness, vigilance, attention and reaction time improve at low (~40 mg) to moderate (~300 mg) doses.
Effects on memory and higher-order executive function (judgment, decision making) are less consistent.
Physical performance effects are evident at doses above about 200 mg (~3 mg/kg).
6Panic attacks in panic disorder patientsMeta-AnalysisCited 42×n=237 · medium study2022
In plain English: The results confirm that caffeine at doses roughly equivalent to 5 cups of coffee induces panic attacks in a large proportion of PD patients and highly discriminates this population from healthy adults.
Klevebrant L et al. · General hospital psychiatry (2022)
The 9 studies investigating panic attacks included 237 patients, of which 51.1% had a panic attack following caffeine, but none after placebo.
Six of these studies compared 128 patients with 115 healthy controls (HC), finding that patients (53.9%) were more vulnerable than HC (1.7%) for panic attacks following caffeine (log RR: 3.47; 95% CI 2.06-4.87).
Six studies investigated subjective anxiety in 121 patients and 111 HC following caffeine, with an overall effect indicating increased sensitivity to the anxiogenic effects of caffeine in the patient group (Hedges' g = 1.02 [95% CI: 0.09-1.96]).