Daniel Perlman’s scientific contributions

... Loneliness, a psychological condition marked by the subjective suffering arising from disparities between desired and actual relationships [7], contrasts with social isolation, an objectively quantifiable variable encompassing aspects such as living alone and limited social ties [8]. These objective and subjective components represent dysfunctional social connections. ...

Reference:

Sex differences in loneliness, social isolation, and their impact on psychiatric symptoms and cognitive functioning in schizophrenia