Cognitive change
Cognitive changes were observed changes in an individual's previous observations, thoughts, resolutions, or recollections. According to Ensign D'Vana Tendi, it was one of the three main symptoms of SMD, which she categorized as changing opinions. 

In 2381, Tendi took note of Ensign Sam Rutherford's new taste for pears, as well as the rekindling of his old relationship with Barnes as indicators of cognitive changes he was experiencing leading her to believe he may have been suffering from SMD. ()
Medical conditions