Precision Depression Adalimumab Trial

The goal of this clinical trial is to learn if the anti-inflammatory medication adalimumab improves depressive symptoms in adults with Major Depressive Disorder (MDD) who are already taking the anti-depressant medication Lexapro (escitalopram). The main questions it aims to answer are: 1. Does adalimumab improve the symptoms of some patients with MDD who are already taking an anti-depressant? 2. What characteristics predict for whom adalimumab has anti-depressant properties. Researchers will compare adalimumab to a placebo (a look-alike substance that contains no drug) to see if adalimumab works to improve depressive symptoms as an add-on drug to the anti-depressant Lexapro (escitalopram). For these primary aims the participants will: 1. Visit the clinic once every 2 weeks for a checkups and injection of adalimumab or placebo from the study psychiatrist (Day 1, 15, 29, and 43 for injections) 2. Complete short (\<5 min) daily surveys for the 57 day duration of the study.