Outreaching activities decrease prognostic accuracy of at-risk mental state defining tools, over-attracting subjects who are not at increased risk of mental illness. The setting was a mental illness primary indicated prevention outpatients service embedded within the Psychiatry Unit of Padua University Hospital, Italy. Help-seeking patients accessing the service between January 2018 and December 2018 were evaluated with validated tools assessing functioning, at-risk mental state, schizotypal personality features, depressive and anxious symptoms, together with medical and family history collection. The primary outcome was the prevalence of drop in functioning at presentation according to the Social and Occupational Functioning Assessment Scale (SOFAS). Secondary outcomes were diagnoses according to DSM-5 criteria and meeting criteria for at-risk mental state. Fifty-nine patients accessed the service, mean age was 18.8 (2.12) years old, 54.2% were females. Virtually all subjects (97.7%) had a drop in functioning. Baseline primary diagnoses were depressive episode in 33%, anxiety disorder in 21%, personality disorder in 17%, adjustment disorder 9%, conduct disorder 7%, schizophrenia spectrum disorder 5%, bipolar disorder 5%, eating disorder in 1.7%, dissociative disorder 1.7%. Overall, 59.1% met at-risk mental state criteria. Lower functioning was associated with anxious symptoms (p=0.031), a family history of mental illness (p=0.045) and of suicide (p=0.042), and schizotypal personality traits (p=0.036). Subjects accessing a prevention service embedded within the mental health department already present a trans-diagnostic drop in functioning, mainly due to a non-psychotic mental disorder, with at-risk mental state in one patient out of two, and schizophrenia or bipolar disorder already present in only 10% of subjects. Prevention service within mental health facility setting appears to properly detect subjects in need of treatment with a drop in functioning, at risk of developing severe mental illness, without any outreaching activity in the general population.