peer reviewed published evidence of their efficacy. of the seven brain training programs that did, only two of those had multiple studies, including at least one study of high quality: brainhq and cognifit. in 2019, a group of researchers showed that claims of enhancement following brain training and other training programs have been exaggerated, based on a number of meta-analyses. other factors, e.g., genetics, seem to play a bigger role. cognitive training for parkinson's disease a 2020 cochrane review found no certain evidence that cognitive training is beneficial for people with parkinson's disease dementia (pdd) or parkinson's disease-related mild cognitive impairment (pd-mci), however the authors also note that their conclusion was based on a small number of studies with few participants, limitations of study design and execution, and imprecise results, and that there is still an overall need for more robust studies involving cognitive training as it pertains to pdd and pd-mci.