Other biological causes could include thyroid dysfunction, blood-suger problems or dysautonomia. Another biological possibility is that you may be experiencing side effects from medication. More often then not, anxiety is the result of a significant psychosocial stressor - a stroke is a big one. Most people, following a stroke, feel an increased sense of vulnerability. You're forced to consider your own mortality and in many cases must give up some of your independence.
Depression is also common following a stroke for many of the same reasons.
Anxiety and depression can be strong catalysts providing the motivation for people to restructure priorities in life and therefore is not necessarily a bad thing. If it persists or reaches an intensity level that makes you question whether or not life is worth living seek professional help. The reader is advised to always seek the advice of their physician prior to changing any treatment or to receive answers to questions regarding a specific medical condition.