ADHD (attention-deficit/hyperactivity disorder) is often associated with overly-active children who can’t sit still or concentrate. But many adults receive ADHD diagnoses later in life, likely because they were able to cope with their symptoms without anyone - including themselves - noticing. So, the uptick in adult ADHD diagnoses isn’t indicative that ADHD can develop later in life—or is it?

Too long; didn’t read

• Adults don’t suddenly develop ADHD, unless it was caused by a severe injury
• It’s possible that new ADHD symptoms are popping up in individuals because they’ve been able to cover or manage them until a stressful event or new demands
• If you think you may have ADHD, mention it to your doctor at your next visit

ADHD 101

Let’s start with the basics. ADHD is a neurodevelopmental condition displaying symptoms of impulsivity, difficulty paying attention, and hyperactivity. According to the Centers for Disease Control and Prevention (CDC), ADHD is one of the most common [childhood] neurodevelopmental disorders.¹

Unfortunately, the research on adult ADHD is lacking. In 2020, 366 million adults dealt with symptoms of ADHD—140 million of which had confirmed ADHD diagnoses in their childhood.² But these statistics could be inaccurate due to the participants' ages. It’s possible that these numbers are much higher in reality.

The bottom line: scientists need to include adults in more ADHD studies.

Adult ADHD diagnosis

To get an ADHD diagnosis, adults need to have at least five inattentive and/or hyperactive symptoms listed in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5). In addition, the symptoms must have been present before the age of twelve.

Untreated childhood symptoms of ADHD can be more noticeable as an adult due to an increase in daily stress and obligations, so it makes sense that many do not seek a formal evaluation until their adulthood. In fact - according to Len Adler, M.D. - at least 75% of adults who have ADHD don’t even know they have the condition.

But where does it come from in the first place?

Researchers are still trying to determine exactly what causes ADHD, but they have some promising leads. 

What causes ADHD?

The exact causes of ADHD are still unknown, but there are several risk factors that scientists are considering. It’s important to note that environmental factors - like screen time or sugar intake - have been disproven and are not directly linked to the onset of ADHD.³

Scientists believe that ADHD could be caused by:

• Genetics
• Traumatic brain injury (TBI)⁴‍
• Premature birth; low birth weight⁵‍
• Early* environmental exposures (e.g. pesticides, lead)
• Substance use during pregnancy

*during infancy in high doses

Can someone suddenly develop ADHD as an adult?

In short - no.

ADHD doesn’t just show up out of nowhere during adulthood. Adults don’t wake up one day and suddenly have ADHD — but it can certainly feel that way.

The stress of adulting can make your ADHD more obvious

Maybe you have a new job that comes with new responsibilities, or perhaps you’re trying to write your dissertation while juggling a toddler and mortgage payments.

Adulting stressors can feel overwhelming—like you no longer have control. And overwhelm can lead to executive dysfunction challenges and cause you to make "careless mistakes."

These small glimpses of your previously-unnoticed ADHD symptoms shine through when you least expect it.

This can be a confusing and frustrating time, and you're definitely not alone. But, if an adult can’t suddenly develop ADHD, what exactly is going on? Why are you experiencing these suspiciously ADHD-like symptoms all of a sudden?

5 possible explanations for newly-developed ADHD symptoms in adulthood

1. You’ve been masking your ADHD all along

You may have had ADHD your entire life—you’ve just managed to hide it until now. This ADHD masking is common in the neurodiverse community, and it’s nothing to be embarrassed about. 

There are several reasons why your mask may have fallen enough for your symptoms to surface. You may have experienced an increase in stress levels or burnout, or your responsibility levels have increased. Whatever the reason, start figuring out how to manage your symptoms by exploring available ADHD resources.

2. Traumatic brain injury (TBI) can cause ADHD (maybe?)

A traumatic brain injury can occur when an object penetrates your head or skull, or when you suffer a heavy blow to the head. In either case, brain tissue is damaged and normal functioning is adversely affected.

TBI is often a result of:

• Falling
• Assault or abuse
• Car accidents (or accidents involving other types of motor/vehicle transportation)
• Sports injuries

A TBI may cause ADHD by changing parts of your brain associated with ADHD, namely the basal ganglia and the prefrontal cortex (PFC).⁶

3. Your thyroid is acting up or your hormones are imbalanced

The thyroid is an important gland that controls a variety of biological and cognitive processes. It’s been shown that irregularly high levels of the hormones that interact with the thyroid are correlated with lower cognitive functioning.⁷ This, in turn, can cause forgetfulness, inattentiveness, and fatigue.

Similarly, hormones directly affect mood and cognition. The main hormones that can interact with (and alter) cognition and executive functioning include:

• Estrogen⁸
• Testosterone
• Dopamine (as a hormone)
• Serotonin (as a hormone)
• Adrenaline 
• Melatonin
• Cortisol⁹

Dysregulated production of any of these can negatively impact how we process new information and respond to our environment. For those without ADHD, it can cause ADHD-like symptoms; for those with ADHD, it can make those symptoms harder to manage.

4. Your untreated ADHD has been exacerbated by the pandemic

The pandemic taught us a lot about our society and ourselves. It also caused a lot of stress and left many of us struggling to keep normal routines. It’s easier to notice little nuances about yourself and your behavior when you’re stuck in the house—and that’s where your ADHD symptoms may have shown through.

If this sounds like you, you’re not alone.

5. You may not have ADHD

Maybe you don’t have ADHD after all! But—that doesn’t mean you aren’t struggling.

Most people experience stress and have some level of difficulty coping with the reality of adulthood at some point in their lives. Some also experience social difficulties, or make poor choices when it comes to coping mechanisms.

But that doesn't mean they have ADHD. 

The fine line between ‘distracted’ and having ADHD

Do you ever walk into a room only to stand there, having no idea why you walked into the room in the first place? Perhaps you’re easily distracted or have trouble concentrating.

ADHD is only diagnosed when it negatively interferes with day-to-day life on a regular basis.

If it’s not ADHD, it could be...

So, what’s causing you to struggle? Maybe one or more of these reasons is to blame:

• Trauma
• Mood or emotional dysregulation‍
• Hormonal shifts, including those related to menopause, contraceptives, puberty, menstruation, hormone replacement therapy, pregnancy, and postpartum
• Lack of sleep (maybe you’re partaking in some revenge bedtime procrastination?)
• Autism
• Increased stress
• Chronic fatigue
• Lack of support
• Another underlying health condition