Fight, Flight or Freeze

Introduce him to positive things in life. Try to show him how to turn negative things into positive ones. Encourage him. Be there for him. Have him vent to you if he needs to. Assure him that you care and that you want to see him be happy. Find things that you both can do together that are encouraging, inspiring, and joyful. Not only will this help him through times of depression, but will also build chemistry in your relationship. And be positive around him, people feed off the emotions of others. Best of luck, I hope this helps! :)

That's not true, Hope. Sometimes it's the people who are in your life most who can help you most. Professionals assist in the diagnosis and diagnosis. Yes, a valuable part they are, but it is also the people around you who help get others on the road to recovery.

Sometimes the best thing you can do is give someone space to calm down and then ask them to write their feelings out. That way they can give it a couple of drafts before having to say "This is what I feel and why I feel that way". Do not be critical of emotions that he's feeling even if you feel they're unfair. Find a way to communicate around the freeze.

respect his thaw time and allow him to work it out in his own mind. When he discovers a way to deal with his stress (if that is in fact the trigger) the freeze should thaw, but dont expect that to happen overnight and dont rush it...you can be supportive by being patientand calm.

He needs more exposure. The more he makes on-the-fly decisions, the less he will freeze up. If there is no time to freeze, he can't. Keep him thinking and mobile.

Having run with someone who does the same? If it's safe to, the first thing I would do is touch him. Just put your hands on his shoulders and hold him there until he starts to unwind. Then very slowly and gently talk him through it. Make sure he's got water to drink if you can, and try and defuse the overload.