Supplementary Material for: The contribution of phenomenology to the assessment of severe non-psychotic forms of psychopathological conditions in transitional age youth

Background: In recent times, adolescents with severe forms of psychopathology that do not unambiguously fit into a precise diagnostic category, have come to clinical observation. The diagnoses attributed to these young patients range from borderline personality disorder, to affective disorders, ADHD, and others. These diagnoses are mainly based on behavioural abnormalities (e.g., social withdrawal, aggressiveness, self-injuring behaviour), but fail to capture the experiential core of their suffering. Summary: Research in psychopathology, particularly that with a phenomenological approach, has long been committed to identifying early markers of schizophrenia in clinical pictures that precede the full onset of this pathology. In this paper, two case studies in Transitional Age Youth (TAY) and additional material taken from our own clinical practice are presented where self-disorders and anomalies of common sense - originally developed to phenomenologically characterise the schizophrenic spectrum phenotype, and especially non-delusional forms of schizophrenia - are used to complement standard nosographic assessments. Key-message: We propose that using some of these phenomenological constructs can shed light on certain TAY pictures, in particular the most serious ones, helping us to grasp their psychopathological core and provide further elements for a fine-grained characterization and in-depth understanding. We propose as a work-in-progress a set of tentative criteria to differentiate such phenomena in TAY patients as compared to patients with a diagnosis of schizophrenia.