Symptoms may be classed into three groups:
Cognitive effects:
mental confusion, hypomania, agitation, headache, coma
Autonomic effects:
shivering, sweating, fever, hypertension, tachycardia, nausea, diarrhea
Somatic effects:
myoclonus/clonus (muscle twitching), hyperreflexia, tremor
Insomnia, sleep disruption, and unrefreshing sleep are also reported symptoms.