Word of advice: research a topic you find interesting! The easiest part of research is locating the right articles--the hardest part is reading and interpreting the data. If you don't find the data interesting, the work will be painful. So again: research a topic you find interesting!
Keywords: psychotherapy, reduce, PPD, ages of 13 and 17
The word reduce is not a MeSH term, but by placing the asterisk * at the beginning of the word (reduc*) will help the database look for the following words: reduce, reduced, reduction, reducing, reduces, etc.