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Psychotic experiences such as hallucinations or delusions have their prevalence peak in childhood and become less prevalent into adolescence, adulthood, and old age. Peters et al in this issue investigated changes in borderline personality disorder (BPD) features across the life span as a potential mechanism underlying the inverse relationship between positive psychotic symptoms and age. Using the data of a large population sample of 19,980 individuals aged between 16 and 95 years they found that BPD features explained 100% of the reduced prevalence of hallucinations and 61% of the reduced prevalence of delusions that occurred with increasing age. General psychopathology explained the inverse relationship between positive psychotic symptoms and age considerably less, suggesting specificity for BPD features in this regard. Remarkably, the mediating effect of BPD features was found in the general population and in a subgroup of participants with a probable psychotic disorder. This suggests that the decline in positive psychotic symptoms with age is indeed explained by changes in BPD features and not (only) by a decrease in the prevalence of psychotic disorders. Even though the study is methodologically sound, future research is required to replicate the findings in a longitudinal study using established measures (preferably clinical interviews instead of screening questionnaires) to assess psychotic symptoms and personality pathology more rigorously. In this paper, we will discuss the results of Peters and colleagues' study from a developmental and transdiagnostic perspective, postulating (a) that positive psychotic symptoms are driven by stressful experiences in individuals with insufficient or maladaptive self-regulation and interpersonal skills, particularly during periods of life that put high demands on the individual (i.e., adolescence), and (b) that positive psychotic symptoms as such can be interpreted as a transdiagnostic, dynamic marker of severity of psychopathology and, in particular, impairment in personality functioning. Applying a dimensional perspective, BPD can be understood as an extreme expression of what lies at the core of personality pathology. According to the alternative model of personality disorder (AMPD) in DSM-5, the core of personality disorders—that is conceptually independent from specific personality disorder types or traits—is defined by marked impairments in self and interpersonal functioning captured by Criterion A. Precursors of BPD may already be evident in childhood. However, (borderline) personality pathology typically first manifests itself in adolescence and can be reliably distinguished from normative adolescent development. The developmental tasks that go along with the transition from childhood to adulthood require competences that come together in Criterion A of the AMPD, that is, identity, self-direction, empathy, and intimacy. Thus, the emergence of personality pathology denotes an adaptive failure to develop competences needed to fulfill adult life tasks. Symptoms of BPD peak in early to late adolescence, and then largely decline over the adult years, with periods of remission and relapse. It is mainly the “acute symptoms” such as affective dysregulation, impulsivity, and self-harming behavior that decrease with age. In contrast, the more “chronic symptoms” such as feelings of emptiness and maladaptive interpersonal functioning often persist over years and characterize BPD in adulthood. Stressful life events and daily hassles may account for the waxing and vanning course of BPD symptoms as they exacerbate negative affectivity in the presence of emotion dysregulation. On the other hand, BPD symptoms themselves can be the generator of stressful experiences that individuals with BPD face such as separation, breakup, and serious problems with close others. Positive psychotic symptoms occur in the general population as well as in clinical samples. Even though they are most prevalent in childhood (with decreasing prevalence rates over the rest of the life span), they become more clinically significant with the transition into adolescence and early adulthood. This means that positive psychotic symptoms in adolescents and young adults are predictive for a wide range of negative outcomes, including the development of psychotic and nonpsychotic mental disorders, multimorbidity, functional impairments, and suicidal behavior. Thus, they are no longer seen as pathognomic for psychotic disorders such as schizophrenia, but may be understood as a transdiagnostic risk maker for severe psychopathology and impairment. In addition, there is increasing evidence suggesting Received: 20 September 2022 Revised: 29 September 2022 Accepted: 1 October 2022