The more the technology is being developed the more medical community is shifting in terminology, from past-referred as mental disorders to the now-labeled organic disorders. There is always a physical (organic) cause to the mental problem rather than being a purely psychic, which mean that it has no relation to the brain-body system.
The old question arise: Does the human have freewill?
To have freewill means to have to possibility to choose. To have no freewill means to be just a random causality of complicated firing chains of neurons in our brain and chemistry of our body.
The secret to freewill is simply the self-awareness. The Self-awareness is a closed loop of consciousness turning upon itself. It may be called Buddha awareness being cultivated through meditation.
Whenever you are anxious and angry try to become self-aware if the your anxiety or anger is rationale or irrational. If you are the type that always find yourself quarreling with others, being always at a bad emotional state, than enter in standing meditation and see how you feel after 30min of meditation. This way you will become aware that regulating your physiology of brain-body system will change your mental state.
In other words, before standing meditation you were unconsciously a pure causality of your physiology without choice. And after the meditation you will be still a causality (cause-effect) of your physiology but with the difference that it was your self-awareness that changed your mental state from angry to a healthy blissful one.