I found anti depressents do block your feelings. personally I think thats the whole problem with them. You actually need to deal with the issues that are causing the depression to break out of the prison (depression). (thats in my case though as I had mild depression).
Is he in rehab for other addictions (drugs).
If so going on anti depressents for a little while is good in order to get past those other addictions and anxieties caused by withdrawel. but a yr is probably long enough.
It's good that he's in rehab. he will probably talk with a therapist or councellor there.