• The research team will check if you are eligible to take part (screening).
• You are only included in screening and the main study if you formally agree to take part (give “informed consent”).
• After giving informed consent, you will be asked some questions about you, your health and your medical history.
• If you are still eligible, a computer will randomly allocate you to one of two groups. There is a 50:50 chance that you may or may not get sertraline. Unless really needed, no one will know for the first 6 months whether you get sertraline or not. If you don't get sertraline, you will get a placebo that looks just the same.
• We will visit you monthly for 6 months and then once at 12 months to ask you how you have been, plus a blood sample taken at 1 month only. If necessary these visits may be done by phone or video call.