Do psychiatrist medications cause extra creaky or weakened joint strength? Can they also cause arthritic symptoms?

A rare side effect. You do't specify the medication - so all one can say is that some do have rare reports of joint pain. Some are actually being prescribed to relieve such pain - and it is not likely to make sense anytime soon. Trust yourself - if you are not able to justify the negative side effects for the help - ask Dr. to get you off that one. Either try another or rely on CBT therapy.