The lifespan continuum of brain disorders: investigating links between neurodevelopmental and neurodegenerative disease—chicken or egg?

Increasing evidence indicates that neurodevelopmental disorders, such as autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), may be linked to a higher risk of developing neurodegenerative diseases, including Parkinson’s disease (PD) and Alzheimer’s disease (AD), later in life. Traditionally, these conditions have been viewed as fundamentally different in their causes, symptoms, and progression. Neurodevelopmental disorders appear early in life, while neurodegenerative diseases usually develop later, often in older age. However, recent research is increasingly highlighting shared molecular mechanisms and pathophysiological features across these disorder groups. Notably, shared processes such as oxidative stress, chronic neuroinflammation, and metabolic dysregulation have emerged as key contributors. Understanding these convergences may open the door to novel, targeted therapeutic strategies. This review critically examines the current evidence supporting potential links between neurodevelopmental conditions such as ASD and ADHD, and neurodegenerative diseases like AD and PD. While some pathological and molecular data suggest overlapping mechanisms, the overall evidence remains mixed and, in many aspects, inconclusive. Although associations between neurodevelopmental disorders and an increased risk of neurodegenerative diseases appear compelling in certain studies, the precise etiological pathways underlying these relationships remain poorly understood. Comorbidities such as depression, chronic stress, metabolic disturbances, and lifestyle-related factors are likely to act as mediators, potentially amplifying vulnerability to cognitive decline, dementia, or parkinsonian features over time. To address these uncertainties, additional epidemiological and clinical research is needed to expand and validate the current evidence base and to clarify the potential links between neurodevelopmental and neurodegenerative conditions.