Synonyms for lethargy

These nouns refer to a deficiency in mental and physical alertness and activity. Lethargy is a state of sluggishness, drowsy dullness or apathy: The war roused the nation from its lethargy.
Lassitude implies weariness or diminished energy such as might result from physical or mental strain: “His anger had evaporated; he felt nothing but utter lassitude” (John Galsworthy).
Torpor and torpidity suggest the suspension of activity characteristic of an animal in hibernation: “My calmness was the torpor of despair” (Charles Brockden Brown). Nothing could dispel the torpidity of the indifferent audience.
Stupor is often produced by the effects of alcohol or narcotics; it suggests a benumbed or dazed state of mind: “The huge height of the buildings . . . the hubbub and endless stir . . . struck me into a kind of stupor of surprise” (Robert Louis Stevenson).
Languor is the indolence typical of one who is satiated by a life of luxury or pleasure: After the banquet, I was overcome by languor.