Final answer:
A predictor of positive response to lithium prophylaxis is the presence of a family history of positive response to lithium, certain genetic markers, and the severity and frequency of mood episodes.
Step-by-step explanation:
A predictor of positive response to lithium prophylaxis in the treatment of mood disorders is the presence of a family history of positive response to lithium. Research studies have shown that individuals who have a family member who was successfully treated with lithium are more likely to benefit from lithium prophylaxis themselves.
Another predictor is the presence of certain genetic markers, such as a variant in the gene GSK3B. Studies have found that individuals with this genetic variant may have a better response to lithium treatment.
Lastly, the severity and frequency of mood episodes can also be a predictor of response to lithium prophylaxis. Individuals who have more severe and frequent mood episodes may have a greater likelihood of positively responding to lithium treatment.