ADHD in Adults (ADD): Complete 2025 Guide to Symptoms & Treatment in NZ

Last updated: 24 September 2025

🧠 What is ADHD in Adults?

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental condition that persists into adulthood for many people. While it is often recognised in childhood, long-term studies show that only a minority of children with ADHD experience full remission in adulthood. Around 10–20% continue to meet full diagnostic criteria, while an additional 40–60% still experience some symptoms and impairment into adult life (Cambridge Neuropsychiatry Review).

Adult ADHD can affect work, relationships, emotional regulation, and overall quality of life.

Research shows that ADHD affects approximately 5% of adults worldwide, yet many remain undiagnosed or untreated (PLOS One – Comorbidity Review). In Aotearoa New Zealand, ADHD medication dispensing among adults increased ten-fold between 2006 and 2022, but significant gaps in diagnosis and treatment remain (NZ Medical Journal). It is estimated that around 200,000 adults in New Zealand may be living with ADHD, although only a small proportion are formally diagnosed and receiving treatment.

Left untreated, ADHD can contribute to long-term risks. A major study led by University College London, published in the British Journal of Psychiatry, found that adults with ADHD face a reduced life expectancy of 4–11 years, largely due to higher rates of accidents, untreated mental health conditions, and substance use (PubMed Central).

Signs and Symptoms of ADHD in Adults (ADD)

ADHD was historically referred to as ADD (Attention Deficit Disorder). Today, ADD is considered an outdated term, but many adults still use it when researching for symptoms, assessments, or treatment. In this guide, we use ADHD and ADD interchangeably.

Core Symptoms

ADHD in adults goes beyond the stereotypes of being “distracted” or “hyper.” While difficulties with attention, organisation, and impulsivity are central, the condition often shows up in ways that are less commonly talked about — but just as important.
Adults may experience:

• Inattention and distractibility – losing focus at work, forgetting appointments, misplacing items, or leaving tasks half-finished.
• Hyperfocus – becoming so absorbed in a stimulating task (e.g., gaming, work projects, or hobbies) that basic needs like eating or sleeping are neglected.
• Poor organisation and time management – struggling to meet deadlines, pay bills on time, or keep routines consistent.
• Impulsivity – acting without thinking, interrupting conversations, overspending, or taking unnecessary risks.

Less often discussed, but equally significant, are the emotional and behavioural aspects of ADHD:

• Emotional dysregulation – intense frustration, sudden mood swings, or angry outbursts are common. Research shows adults with ADHD have significantly greater difficulty regulating emotions than neurotypical adults (Shaw et al., 2014 – Journal of Affective Disorders).
• Aggression and irritability – some studies link ADHD in adults with higher rates of verbal or physical aggression, especially when combined with stress or comorbid conditions (Surman et al., 2013 – CNS Spectrums).
• Rejection sensitivity – feeling devastated or enraged by perceived criticism or rejection, sometimes described as Rejection Sensitive Dysphoria.
• Poor self-care – forgetting to eat, neglecting hygiene, or struggling to maintain daily routines.
• Sleep disruption – staying up late, difficulty winding down, or irregular sleep cycles.
• Relationship strain – partners and colleagues may misinterpret forgetfulness, irritability, or missed commitments as a lack of care, when these are often direct consequences of ADHD.

These symptoms can sometimes lead to guilt, shame, or conflict in daily life — especially because there is still stigma attached to certain behaviours like anger, forgetfulness, or poor self-care. It’s important to remember that these are recognised features of ADHD in adults, not personal failings. If you recognise some of these patterns in yourself, seeking a psychiatric assessment can provide clarity and open the door to treatment and support that helps you manage them more effectively.

Associated Conditions and Comorbidities

ADHD rarely occurs in isolation. Studies show that up to 80% of adults with ADHD have at least one additional psychiatric condition, most commonly depression, anxiety, personality disorders, or substance use disorders (PLOS One – Comorbidity Review).

There is also a strong link between ADHD and trauma. A recent systematic review found that 28–36% of adults with ADHD also meet criteria for Post-Traumatic Stress Disorder (PTSD), and this combination is associated with more severe functional impairment and complex treatment needs (Systematic Reviews Journal – ADHD & PTSD).

In addition to psychiatric comorbidities, several medical conditions can mimic ADHD symptoms, including sleep disorders and thyroid dysfunction. Sleep issues such as sleep apnoea are well-known contributors to inattention and fatigue, while both hypothyroidism and hyperthyroidism can cause “brain fog,” poor concentration, and memory difficulties (Healthline – ADHD Misdiagnosis).

This is why an ADHD diagnosis must go beyond symptoms. When a psychiatrist performs a First Specialist Assessment (FSA) or psychiatric consultation, they are not simply evaluating your mental health in isolation. The first session takes a holistic view of your medical, psychiatric, and personal history — ruling out other possible explanations (such as thyroid conditions, sleep disorders, or trauma), considering co-existing conditions, and assessing your overall wellbeing. Based on this comprehensive picture, the psychiatrist then decides whether a formal ADHD assessment is appropriate.

Causes of ADHD & Risk Factors

The exact causes of ADHD in adults are not fully understood. What is clear, however, is that ADHD often runs in families, which shows that genetics play a major role. A Swedish study that followed 1,480 twin pairs from childhood into adulthood showed that the differences in attention problems between people could largely be explained by genetic factors rather than environment, confirming that ADHD has a strong hereditary basis (JAMA Psychiatry, 2013). Other large studies have found that children of parents with ADHD are more than eight times as likely to be diagnosed with the condition compared with children whose parents do not have ADHD (Uher et al., 2023 – World Psychiatry). Reviews of multiple studies estimate that genetics account for around 70–80% of the likelihood of developing ADHD (Faraone & Larsson, 2019).

Certain risk factors may increase the likelihood of ADHD or worsen symptoms, including:

• Being born prematurely or with low birth weight
• Prenatal exposure to nicotine, alcohol, or other substances
• Early exposure to high stress or trauma
• Family history of ADHD or other mental health conditions

ADHD in Adults: Diagnosis and Testing in NZ

An ADHD test for adults is not just a checklist — it is a comprehensive psychiatric evaluation that considers medical history, symptoms, and any co-existing conditions. This ensures the diagnosis is accurate and that treatment is safe and effective.

Getting an ADHD diagnosis in adults in New Zealand can be confusing because different professionals play different roles. Psychologists can complete testing and provide reports, which may be helpful for supporting applications for school or workplace accommodations, but they cannot prescribe ADHD medication. For adults, only a psychiatrist can formally prescribe and manage treatment, while for children this role can be undertaken by either a psychiatrist or paediatrician. Psychologists still play an important role, particularly in providing therapy and behavioural support, but most adults will still need to see a psychiatrist to access medication.

Access through the public health system (via Health New Zealand/Te Whatu Ora hospitals) is very limited. Referrals to public psychiatry services are usually restricted to the most severe cases, and even then waitlists can extend many months or even years. For most adults, pursuing a private ADHD assessment in NZ is the only realistic option.

It is also important to be aware of the potential for “double-paying.” Some patients pay for a psychologist’s ADHD assessment, only to later be told they must also see a psychiatrist before medication can be considered.

In New Zealand, ADHD medication can only be initiated by certain specialist doctors. For children, this is usually a paediatrician or psychiatrist; for adults, a psychiatrist (NZ Gazette). This restriction is outlined in the Ministry of Health’s Special Authority criteria, which ensure that all prescriptions are carefully reviewed and clinically appropriate. Generally speaking, the most efficient way for an adult to be diagnosed with ADHD in New Zealand is through a private psychiatrist in the first instance. If a diagnosis is made, the psychiatrist and patient can then explore whether medication is an appropriate part of the treatment plan.