Sure agree that lack of confidence can be a big factor to kick start some underlying factors of anxiety, panic, depression, ocd, etc. There may be organic origins, but also experiential, environmental, psych factors affecting it.
With weak or no confidence miseries such as fear, worries, uncertainties, etc. or guilt, as AM suggests, can find fertile territory to grow and start to take over. "Be Confident" is definitely one of my mantras in meditation. Guilt has always been huge with me, always a struggle.