It has in fact been shown in countless studies that corticosteroids (stress hormones that are released in situations like the ones I described in the article) cause cognitive deficits in humans and other animals. Here is one slightly strange example:

The present study investigated the acute effects of cortisol administration in normal healthy male volunteers on immediate free recall and recognition of pleasant, unpleasant, and neutral nouns using a between-subjects double-blind design. Two hours after cortisol (10 mg) or placebo administration, impaired recall and recognition of neutral and pleasant words was found in the treatment group, whereas recall and recognition of unpleasant words was similar in both groups.

See: http://ukpmc.ac.uk/abstract/MED/12820857/reload=0;jsessionid...