The Intersection of Neurology and Psychiatry: Insights into Neuropsychiatry in Neurodegenerative Disorders View PDF

Neurology and psychiatry, though traditionally considered separate medical disciplines, are increasingly recognized as interdependent fields with significant overlap (Table 1 and figure 1) [1]. Neurology focuses on the structural and functional disorders of the nervous system, while psychiatry delves into the complexities of mental health and behavior [2]. Emerging research underscores the intricate interplay between brain structure, neurochemical processes, and mental health disorders, demonstrating that many psychiatric conditions have neurological underpinnings [3]. For example, up to 35% of patients with PD experience clinical depression [4], and cognitive impairments are a hallmark feature of AD, illustrating how neurodegenerative processes profoundly affect mental health [5]. The growing prevalence of such disorders demands a collaborative approach to better understand and manage these complex conditions.

Recent epidemiological data highlight the burden of comorbid neurological and psychiatric conditions on global health systems. According to the World Health Organization (WHO), neuropsychiatric disorders contribute to 10% of the global burden of disease, and depression alone is the leading cause of disability worldwide, affecting over 280 million people [6]. Dementia affects more than 55 million people worldwide, with AD being the most common cause, accounting for 60 to 70% of cases [7]. Psychiatric manifestations such as apathy, depression, and psychosis occur in over 50% of dementia patients, significantly impacting their QoL and caregiving demands [8]. Similarly, approximately 25 to 50% of individuals with HD experience severe psychiatric symptoms, including depression and suicidal ideation, often preceding the onset of motor symptoms [9]. These statistics underscore the profound societal and economic toll of neurodegenerative and psychiatric disorders, emphasizing the urgency of addressing their overlapping aspects. Furthermore, conditions like multiple sclerosis (MS) and epilepsy frequently exhibit psychiatric comorbidities such as anxiety and depression, with rates as high as 50% in some patient populations [10]. This convergence of neurology and psychiatry emphasizes the need for integrative care models, where clinicians from both disciplines work together to address the overlapping symptoms and improve outcomes for patients.

Advances in neuroimaging and molecular biology have provided deeper insights into the shared mechanisms between neurological and psychiatric disorders. Techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) scans have revealed abnormal brain activity patterns in conditions like schizophrenia, where disrupted connectivity between brain regions mirrors structural abnormalities seen in neurodegenerative diseases [11]. Moreover, genetic studies have identified common risk factors, such as the APOE-ε4 allele, which is implicated in both AD and lateonset depression [12]. These findings support the idea that neurological and psychiatric disorders are not isolated phenomena but rather different manifestations of shared pathophysiological processes, further blurring the lines between the two disciplines.

Understanding the interplay between neurology and psychiatry also has critical implications for treatment. Disorders like chronic pain, for instance, are now recognized as both neurological and psychiatric, requiring a multimodal approach that includes pharmacological, cognitive-behavioral, and rehabilitative therapies [13]. Similarly, the management of stroke patients increasingly incorporates psychiatric screening, as one-third of stroke survivors develop post-stroke depression, which negatively impacts recovery and QoL [14]. As the fields of neurology and psychiatry continue to converge, adopting a holistic approach to diagnosis and treatment will be essential to addressing the complex needs of patients with overlapping symptoms.