Final answer:
The priority nursing diagnosis for a client with OCD is 'Anxiety related to obsessive thoughts as evidenced by ritualistic behaviors,' as it directly addresses the core of the obsessive-compulsive cycle, where anxiety leads to compulsions.
Step-by-step explanation:
The priority nursing diagnosis for a client newly admitted to an in-patient psychiatric unit with obsessive-compulsive disorder (OCD) should address the most significant and immediate impact of the condition on the individual's well-being. Among the options provided, the diagnosis that often takes precedence is Anxiety related to obsessive thoughts as evidenced by ritualistic behaviors because the anxiety experienced by individuals with OCD usually drives the compulsive behavior and sets a foundation for other symptoms.
Option 1) Anxiety R/T obsessive thoughts AEB ritualistic behaviors accurately captures the essence of the obsessive-compulsive cycle. The obsessive thoughts provoke considerable anxiety, which the patient attempts to alleviate or manage through the performance of ritualistic behaviors or compulsions.
While Powerlessness, Fear, and Social isolation may also be relevant nursing diagnoses, the immediate concern in OCD often centers on the management of anxiety, which is the underlying cause of the other symptoms. As such, addressing the anxiety should ideally help mitigate the other associated problems like social isolation or feelings of powerlessness.