Irene occasionally experiences unpredictable episodes of intense dread accompanied by chest pains and a sensation of smothering. Since her symptoms have no apparent cause, they would probably be classified as indicative of:

Irene must be suffering from some phobia or a panic attack.

Explanation:

Panic attack are sudden instances when a person experiences extreme fear.

During panic attacks, a persons various physical reactions are triggered.

A panic attack has no apparent cause.

Common symptoms include: numbness, loss of control , increased heart rate, feeling of chest congestion, breathlessness etc.

Panic attacks can  prove to be fatal.

answer; /// i do believe its (heredity); good luck

answer by yourhope:

answer is

human impact on the environment can be seen in the deterioration of the !

: )