Why is Adult ADHD Difficult to Diagnose?

Summary: The primary reason adult ADHD is difficult to diagnose is that for decades, the consensus among most people was that only children and adolescents could receive a clinical diagnosis for ADHD. This mistake, which created a false cultural/social norm, led to a significant number of problematic consequences for both adults with ADHD and the providers who can support them.

Key Points:

• People with ADHD who didn’t receive a diagnosis during childhood or adolescence may have developed a wide range of strategies to manage their neurological differences, without knowing they actually had diagnosable neurological differences.
• Adults with ADHD may have sought support – without success or resolution – for other mental health disorders.
• Since ADHD is a neurodevelopmental disorder, symptoms must first appear in childhood, and many adults with ADHD may suspect – but can’t confirm unequivocally – that their symptoms first began during childhood.

About Adult ADHD

First, let’s make something clear:

Adults can and do receive ADHD diagnoses.

A study called “The Changing Prevalence of ADHD? A Systematic Review” cites a large range of prevalences reported in studies around the world. Estimates varied from five percent to 47 percent, with two reliable studies reporting a believable range – worldwide – of between five and seven percent.

In addition, a study published in 2023 used verified data from the Centers for Disease Control (CDC) to determine the prevalence of ADHD among adults in the U.S. Here’s what they found:

ADHD in 2023: Adults 18+

• Total: 6% (15.5 million)
• By specific age group:
  • 18-24: 21.7%
  • 25-29: 62.8%
  • 50-64: 10.6%
  • 65+: 4.9%

The data shows that ADHD among adults is far more common than most people suspected just ten years ago. In addition, researchers gathered data on the age at which individuals received a diagnosis. Here’s what they found:

ADHD: Age at Diagnosis

• Before 18: 44.1%
• After 18: 55.9%

That information may come as a surprise to most people. It shows that among people with ADHD in 2023, more than half received a diagnosis during adulthood. Although many of those people report symptom onset during childhood, this debunks the notion that most people with ADHD receive an ADHD diagnosis during childhood or adulthood, and if you didn’t receive a diagnosis as a child or adolescent, you probably don’t have ADHD.

How Does Adult ADHD Appear?

We should make another thing perfectly clear:

While online self-tests and feeling sympatico with TikToks, Facebook, and Instagram posts about adult ADHD may make you 100% sure you have ADHD, only a qualified mental health professional can give you a clinical diagnosis of ADHD.

That’s important because people who want the most effective, first-line treatments for ADHD – i.e. prescription medication – need a clinical diagnosis before they can receive a prescription for effective ADHD medication.

The symptoms of ADHD in children and adolescents revolve around inattention, impulse control, and hyperactivity in more than one life domain – i.e. home and school, school and sports practice, music lessons and school – and must first appear during childhood. While similar criteria apply to adult diagnosis – persistent disruption in more than one life domain – the way inattention, impulse control, and hyperactivity shows up in adults is often different than how it shows up in kids and teens.

Here’s what the symptoms of ADHD might look like in an adult:

• Impaired/inconsistent work performance
• Changing/quitting/losing jobs regularly
• Inconsistent academic performance and/or achievement: lower grades than expected, dropping out of degree/other programs
• Difficulty managing tasks at home: paying bills, staying organized, managing time
• Issues in relationships caused by difficulty following through on tasks or commitments
• Extreme and sometimes debilitating procrastination
• Forgetting key deadlines
• Becoming angry/upset of small things
• Stress caused by problems meeting responsibilities and commitments
• Persistent feelings of guilt, self-blame, and frustration

To learn whether they meet criteria for a clinical ADHD diagnosis, adults need to seek a full evaluation from a mental health professional. The primary reason for that – aside from the need for evidence-based treatment, which requires a diagnosis from a physician – is the fact that ADHD commonly occurs with other mental or behavioral disorders, and accurately identifying symptoms requires a high level of training and experience.

Adult ADHD and Difficulty With Diagnosis: Co-Occurring Disorders, Self-Management

In a recent interview on adult ADHD diagnosis published by the Journal of the American Medical Association (JAMA) called “The Challenge of Diagnosing Adult ADHD,” editors point out that many people with ADHD have a co-occurring mental health disorder.

Here are the facts on ADHD and co-occurring mental health disorders:

• 70% have another mental or behavioral disorder
• 50% have anxiety
• 20% – 50% have depression
• 7%a – 11% have bipolar disorder

The reason co-occurring disorders can make adult ADHD difficult to diagnose is that the symptoms of ADHD often overlap with the symptoms of anxiety disorders and mood disorders. An adult with ADHD may spend years – literally – seeking support for depression and anxiety, but not see any improvement in their core symptoms or challenges. They may try antidepressant, anxiolytics, and mood stabilizers, but still have the same problems at home, at work, and in relationships.

This can be incredibly frustrating, and cause an adult with ADHD to lose hope, lose self-esteem, and lose the belief that they’ll every succeed at work, with time management, or simply remembering things they need to remember.

In addition, it’s not unusual for a person with ADHD to attempt to manage symptoms – and frustration, depression, and anxiety about symptoms – with alcohol or drugs through the practice of self-medication.

That never really works well at all.

In fact, self-medication can lead to substance use disorder (SUD), a mental health diagnosis on its own, with its own set of symptoms and serious negative consequences, and exacerbate any pre-existing, co-occurring mental health disorder.

So what should an adult who thinks they have ADHD do about it?

Professional Support and Full Psychiatric Evaluation

A qualified mental health professional is trained to understand the challenges in diagnosing adult ADHD and equipped with the tools to overcome those challenges. Therefore, the most important thing for an adult dealing with the symptoms we list above – severe procrastination, chronic forgetfulness, inability to follow through on work, home, and school projects – is to seek full evaluation from a mental health professional.

During the evaluation, it’s essential to:

• Be open and honest about all symptoms
• Discuss the emotional impact of managing symptoms
• Talk about work, relationships, and family history
• Address school experiences, i.e. being bored with material, understanding concepts but unable to complete assignments
• Talk openly about anxiety, depression, shame, or guilt, however they may appear

One thing that can happen during or after an evaluation is that a psychiatrist or therapist can give a name, a context, and a reason for many of the things that have caused problems for an adult with ADHD for years.

This often leads to a lightbulb moment.

The provider has an objective perspective, and when they offer it – often in the form of a diagnosis – the adult under evaluation looks back over their years without a diagnosis and says:

“This explains so much of my life. I wish I’d gotten evaluated years ago.”

A diagnosis and an insight won’t immediately solve every problem an adult with ADHD faces, but this lightbulb moment can be a huge relief. And what happens next – treatment with medication, the development of specific skills to manage specific symptoms/differences – can indeed be lifechanging. It takes work, awareness, and understanding, but an adult with a new ADHD diagnosis can learn to manage their differences and succeed and excel in ways that  can improve their overall mental, physical, social, and emotional health and wellness.