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.