Creatine supplementation is neuroprotective and enhances health and lifespan in mice (1).
The impact on the mouse brain is consistent with the beneficial effects of creatine supplementation on human cognition.
In my opinion, creatine is a low-risk, high-reward supplement for improving brain health with substantial supporting human evidence. For example, see: (2).
Benefits of creatine on cognition are likely to be very modest but may accrue over time.
Vegetarians and vegans get no creatine from their food, while the average omnivore gets about 1 g/d. Several studies have suggested that vegetarians and vegans see greater benefit from creatine supplementation than do omnivores. This may be because of low baseline intake.
I estimate that non-athletes would benefit from intakes of around 3 g/d.
We really need large, rigorous, long-term clinical trials to confirm the findings of these smaller trials.
In the meantime, creatine is extremely safe and can provide only benefits to physical and probably mental performance (especially under stressed conditions).
You can purchase creatine monohydrate, a very inexpensive but effective form of creatine, at my affiliate link here: https://refer.link/cKGR