R. v. Nystrom, 2023 BCCA 232, June 8, 2023, at paragraphs 21 and 22:

A medically recognized mental disorder such as cognitive impairment, which has caused or contributed to the commission of an offence, may be a mitigating factor that reduces an offender’s moral culpability and thereby warrants a reduction in sentence. In these circumstances, both general and specific deterrence will necessarily play a diminished role in determining a fit sentence: R. v. Badhesa, 2019 BCCA 70 at para. 42; R. v. Penttila, 2020 BCCA 63 at paras. 68–69.

Sentencing judges must consider evidence of the nature and magnitude of the disorder, determine its overall role in the offending conduct, and be satisfied on a balance of probabilities that the disorder caused or contributed to the commission of the offence. Detailed and specific medical evidence is necessary to properly understand the relationship between the disorder and the offending conduct; generalized evidence is not sufficient.