"Cognitive" is the word that fills the blank efficiently.
Cognitive abilities are very important for the psychological quality of an individual, as well as for stimulating their abilities and talents.
Therefore, the complete sentence would be "Previous patients have described how art therapy activities have improved their Cognitive skills and ability to process trauma and confront issues relating to frustrations, transitions, and grief."
Learn more about cognitive ability at the link:
https://brainly.com/question/18994513
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