Focus, processing speed and mental fatigue are increasingly part of wellness conversations. TMS research offers a more nuanced look at whether brain stimulation can influence cognitive performance.
Modern life places a constant demand on attention. Switching between messages, meetings, screens and decisions can leave people feeling mentally overloaded, unfocused or simply drained. Terms such as “brain fog” and “mental fatigue” are now part of everyday language, but cognition is not one single function. Attention, executive function, processing speed and memory rely on partly distinct processes and networks.
TMS has been investigated across these cognitive domains, including in healthy adults. A systematic review and meta-analysis by Xu et al. included 53 randomized studies and 1,507 healthy participants. Offline high-frequency rTMS, meaning stimulation delivered before cognitive testing, was associated with small effects on overall cognitive accuracy and reaction time. Small effects were also reported for executive function, while attention-specific effects were not statistically significant. [1] That distinction is important. The findings support the possibility of modest, protocol-dependent cognitive modulation rather than a broad “cognitive enhancement” effect. [1]
What do clinical studies add?
Research in clinical populations provides additional clues about the cognitive systems that may be responsive to stimulation. In ADHD, a meta-analysis of randomized trials reported improvements in sustained attention and processing speed, while memory and executive-function effects were not statistically significant. Because these participants had ADHD, the findings cannot simply be extrapolated to healthy adults. [2]
A systematic review and meta-analysis in mild cognitive impairment, Alzheimer disease and related cognitive disorders also found evidence of cognitive effects across TMS studies, although differences in populations, protocols and outcome measures limit simple generalization. [3]
What about brain fog and mental fatigue?
Small studies in long COVID have explored rTMS for fatigue and cognitive dysfunction. Sasaki et al. treated 12 patients with ten sessions of high-frequency rTMS and reported changes in fatigue and cognitive outcomes, while Noda et al. reported real-world outcomes in long-COVID neuropsychiatric symptoms. These studies are hypothesis-generating rather than definitive sham-controlled efficacy trials. [4,5]
Complementary research using electrical forms of non-invasive brain stimulation has also examined experimentally induced mental fatigue in healthy adults. In a small study of 10 young adults, both anodal tDCS and alpha-frequency tACS were associated with lower subjective fatigue and improved task accuracy compared with a blank-control condition. Because this was electrical rather than magnetic stimulation, it should be viewed as supporting context rather than direct evidence for TMS. [6]
So can TMS make us sharper, faster or more focused? The current science does not support a universal “brain boost.” What it does show is that non-invasive stimulation can interact with cognitive systems, and that the size and direction of the effect depend on the person, brain target, protocol and task. That makes mental clarity and cognitive performance an exciting area of research.
References
[1] Xu M, Nikolin S, Samaratunga N, et al. Cognitive Effects Following Offline High-Frequency Repetitive Transcranial Magnetic Stimulation (HF-rTMS) in Healthy Populations: A Systematic Review and Meta-Analysis. Neuropsychol Rev. 2024; 34(1):250-276. doi:10.1007/s11065-023-09580-9.
[2] Chen YH, Liang SC, Sun CK, et al. A meta-analysis on the therapeutic efficacy of repetitive transcranial magnetic stimulation for cognitive functions in attention-deficit/hyperactivity disorders. BMC Psychiatry. 2023; 23(1):756. doi:10.1186/s12888-023-05261-2.
[3] Pagali SR, Kumar R, LeMahieu AM, et al. Efficacy and Safety of Transcranial Magnetic Stimulation on Cognition in Mild Cognitive Impairment, Alzheimer Disease, Alzheimer’s Disease Related Dementias, and Other Cognitive Disorders: A Systematic Review and Meta-Analysis. Int Psychogeriatr. 2024; 36(10):880-928. doi:10.1017/S1041610224000085.
[4] Sasaki N, Yamatoku M, Tsuchida T, et al. Effect of Repetitive Transcranial Magnetic Stimulation on Long Coronavirus Disease 2019 with Fatigue and Cognitive Dysfunction. Prog Rehabil Med. 2023; 8:20230004. doi:10.2490/prm.20230004.
[5] Noda Y, Sato A, Shichi M, et al. Real world research on transcranial magnetic stimulation treatment strategies for neuropsychiatric symptoms with long-COVID in Japan. Asian J Psychiatr. 2023; 81:103438. doi:10.1016/j.ajp.2022.103438.
[6] Chen R, Huang L, Wang R, et al. The effect of transcranial electrical stimulation on the relief of mental fatigue. Front Neurosci. 2024; 18:1359446. doi:10.3389/fnins.2024.1359446.
