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He is showing the features of anxiety disorder called Agoraphobia
along with non specific anxiety. As he is 78 so he might showing symptoms due to Alzheimer's disease. But other features like memory impairment, cognitive decline etc are also observed. His thyroid
levels may be a cause of anxiety but there are not in extreme ranges. As he is in distress I will advise you to take him to a good psychiatrist
for expert opinion. Medicines like Propranolol
can be given in low doses. Other medicines like Sertaline are also useful and have proven results in anxiety in elderly. And above all proper warm support and care is must for him.
Dr. Seikhoo Bishnoi