Instructions: Given a passage with a question and an answer to that question, classify if the answer actually answers the question into 'yes' or 'no'. Output 'yes' if the answer answers the question and output 'no' if the answer does not answer the question.
Input: Question: Are lower serum brain-derived neurotrophic factor levels associated with failure to achieve remission in patients with major depression after escitalopram treatment?
Answer: This study included a small sample, and measured serum BDNF levels in the MDD patients at only one point during the maintenance treatment.
Output:
yes