Trust in the therapist also matters and I suppose that is dependent on a lot of factors such as time spent with them, your satisfaction with how you feel after a decent number of sessions, how vulnerable you feel to opening up. Since we have experienced traumatic events, maybe it takes more time to feel comfortable opening up. I usually felt like talking in general, then going into specifics as I felt more comfortable. If we repress or hold back, it has a way of re-surfacing in some other session/conversation.