"Laughing 'fit to burst' has been found to cause possible heart rupture, a torn gullet and epileptic seizures. A quick intake of breath during laughing can provoke an asthma attack, while some people have suffered from incontinence and even hernias.'
'The presumed positive effects of laughter on wellbeing have been harnessed in serious mental disorders, without much evidence of benefit. Some psychoanalysts believe that a joke can substitute for interpretation—provided that the patient appreciates the joke. Others, however, view jokes as undesirable, because they circumvent resistance to psychic exposure and may be regarded as seductive.'
'Researchers also found beneficial effects, including the lowering of blood sugar in diabetic patients and reducing arterial wall stiffness, which helps relieve tension. The researchers say their findings challenge the view that laughter can only be beneficial but do add that humour in any form carries a ‘low risk of harm and may be beneficial’. ‘It remains to be seen whether sick jokes make you ill, dry wit causes dehydration or jokes in bad taste [cause] dysgeusia (distortion of sense of taste),’ they said. The paper was published in the Christmas edition of The British Medical Journal.'"