Does depression affect sex drive?

Yes: There are various possible reasons for this, including, but not limited to a general malaise, decreased energy, and a desire to avoid people.

Depressive syndrome: Depression is a syndrome which comprises multiple symptoms that are interrelated but untrained people may thing each symptom un-related to each other. Not all symptoms are obliged to be present for the diagnosis. Loss of sexual desire is one of the main symptom. Other people has normal sexual desire but has other symptoms of depression. Search "symptoms of depression".

Depression and sex: Depression affects a lot of things, including sex drive, or libido. Some antidepressant medications can also affect sex drive. Best thing to do is get a psychiatric consultation to find out if it's depression, unless that's already been done, and then go from there. Mental health practitioner's can also help with depression, and ways to get one's general energy level up and moving again.