This chapter provides a brief overview of medical and neurological conditions such as chronic fatigue syndrome, postural tachycardia, and traumatic brain injuries. These are clinically relevant as their symptoms significantly overlap with ADHD, thus complicating the diagnostic process and adversely affecting the overall prognosis if these remain untreated. Moreover, similar to ADHD and other NDD, these conditions present with a wide range of symptoms, mostly not filling discrete diagnostic criteria; hence, the correct diagnosis is missed in several cases. It is common for these patients to visit multiple emergency rooms or urgent care facilities, undergoing many tests and procedures to find the right diagnosis. Sadly, some might be labeled as “psychosomatic” or even suspected of malingering symptoms for secondary gain. These conditions are relevant for clinical discussion in this book. During pregnancy and the postpartum period, symptoms may worsen secondary to intense hormonal changes, metabolic issues, malnutrition, and sleep disturbances. These issues worsen pre-existing neurocognitive symptoms and emotional instability as well. Subsequently, the chapter addresses diagnostic and treatment challenges for pregnant and postpartum mothers who suffer from dual diagnosis, i.e., the coexistence of substance use disorders, psychiatric illnesses, and neurodevelopmental issues, as well as the comorbidity of ADHD and ASD in some individuals.