malaise

affection, affliction, ail, ailment, bug, complaint, complication, condition, disease, disorder, distemper, distemperature, dysfunction (also disfunction), fever, ill, illness, infirmity, malady, sickness, trouble, upset

matter, pip

indisposition, unhealthiness, unsoundness

sickishness

debilitation, debility, decrepitude, feebleness, frailness, frailty, invalidism, invalidity, lameness, sickliness, weakliness, weakness

hebetude, languor, lassitude, lethargy, listlessness, stupor, torpor

hypochondria

attack, bout, fit

angst

agita, agitation, anxiety, anxiousness, apprehension, apprehensiveness, care, concern, concernment, disquiet, disquietude, unease, fear, nervosity, nervousness, perturbation, solicitude, sweat, uneasiness, worry

fearfulness, torment, upset, vexation

strain, stress, tension

alarm (also alarum), anguish, consternation, desperateness, desperation, discomfort, discomposure, dismay, distraction, distress, disturbance, edginess, franticness, hand-wringing, jitters, jumpiness, panic, tremor

blue devils, blues, depression, desolation, despond, despondence, despondency, disconsolateness, dispiritedness, doldrums, dolefulness, downheartedness, dreariness, dumps, forlornness, gloom, gloominess, glumness, heartsickness, joylessness, melancholy, miserableness, mopes, mournfulness, oppression, sadness, sorrowfulness, unhappiness

cold feet, doubt, dread, foreboding, incertitude, misgiving, presentiment, suspense, uncertainty

compunction, qualm, scruple