Care, concern, solicitude, anxiety, worry are comparable when meaning either a state of mind in which one is engrossed and troubled by something pertinent to oneself or another, or the pertinent thing that engrosses and troubles one. The same distinctions in implications and connotations are evident in their corresponding adjectives (careful, concerned, solicitous, anxious, worried) when they mean engrossed and troubled by a particular matter.
Care and careful (which is archaic in this sense; see also CAREFUL 2) imply preoccupation and oppression of mind because of heavy responsibilities or disquieting fears or apprehensions.
Concern and concerned stress absence of indifference, but they also imply a degree of care because of one's interest, affection, respect, or responsibility.
Solicitude and solicitous imply profound concern; sometimes they connote extreme apprehensiveness, but more often they suggest thoughtfulness for another's welfare, well-being, or success and sometimes an almost hovering attentiveness in another's misfortune.
The last two pairs of words in this group imply far more agitation and depression than the first three.
Anxiety and anxious stress the anguish of fear coupled with uncertainty or of the anticipation of impending failure, misfortune, or disaster.
Worry and worried usually suggest more mental activity, often futile, than anxiety and anxious or more fretting or stewing over problems or situations or persons that are a cause of solicitude or anxiety.