Adult ADHD: Why 90% Have Other Diagnosed Health Conditions

The true cost of a missed diagnosis is rarely just a missing label; it is a lifetime of accumulated psychological erosion. Recent insights from the Irish College of General Practitioners (ICGP) reveal a stark reality: for the vast majority of adults with ADHD, the disorder does not travel alone. Instead, it arrives with a heavy baggage of comorbidities—sleep disorders, chronic anxiety, and profound mood instability—that are often the direct result of spending decades attempting to navigate a world not built for their neurobiology.

The Deep Dive: The Cycle of Late Diagnosis

For years, the clinical archetype of ADHD was the hyperactive young boy. This narrow lens created a systemic blind spot for women and those whose struggles were internal rather than external. Dr. Aoife O’Sullivan, clinical lead for mental health at the ICGP, suggests that the high prevalence of anxiety and sleep issues in adults isn’t necessarily a coincidental pairing, but a secondary consequence. When a person spends years “masking” their symptoms—working twice as hard as their peers to achieve “normal” results—the resulting chronic stress manifests as generalized anxiety and “cognitive insomnia,” where the brain refuses to shut down despite physical exhaustion.

The stakes of this diagnostic lag are devastatingly high. Data from ADHD Ireland indicates that 20% of adults with ADHD have attempted suicide and 50% have engaged in self-harm. This suggests that the “mood disorders” often treated in isolation may actually be symptomatic of an unaddressed neurodevelopmental foundation. Furthermore, the emergence of Rejection Sensitivity Dysphoria (RSD) adds a layer of emotional volatility that complicates interpersonal relationships and workplace stability, further isolating the undiagnosed adult.

Parallel to this mental health shift is a transformation in women’s physical health. The surge in Hormone Replacement Therapy (HRT) usage—rising from 80,000 items in 2020 to over 240,000 in 2022—signals a departure from the restrictive prescribing habits of previous decades. More importantly, the shift from oral oestrogen to transdermal options (patches, gels, and sprays) reflects a modern, evidence-based approach to safety, reducing risks while improving the quality of life for women entering menopause.

The Forward Look: Integrated Health Screening

Moving forward, we should expect a convergence in how primary care handles neurodiversity and hormonal health. There is a growing clinical recognition that menopause can exacerbate ADHD symptoms (or mimic them via “brain fog”), potentially leading to a new wave of women seeking neurodevelopmental screenings during the perimenopausal transition.

Medical practitioners will likely move toward a “holistic screening” model. Rather than treating insomnia or anxiety as standalone issues, GPs will be encouraged to look for the underlying neurodivergent patterns that may be driving these comorbidities. As the “masking” generation of women and quiet men comes forward, the healthcare system must shift from a reactive model—treating the depression and anxiety—to a proactive model that addresses the root cause: the ADHD itself.