April 7, 2021

Adult Onset ADHD: Does it Exist? Is it Distinct from Youth Onset ADHD?

There is a growing interest (and controversy) in 'adult-onset ADHD. No current diagnostic system allows for the diagnosis of ADHD in adulthood, yet clinicians sometimes face adults who meet all criteria for ADHD, except for age at onset. Although many of these clinically referred adult-onset cases may reflect poor recall, several recent longitudinal population studies have claimed to detect cases of adult-onset ADHD that showed no signs of ADHD as a youth (Agnew-Blais, Polanczyk et al. 2016, Caye, Rocha, et al. 2016). They conclude, not only that ADHD can onset in adulthood, but that childhood-onset and adult-onset ADHD may be distinct syndromes(Moffitt, Houts, et al. 2015)

In each study, the prevalence of adult-onset ADHD was much larger than the prevalence of childhood-onset adult ADHD). These estimates should be viewed with caution.  The adults in two of the studies were 18-19 years old.  That is too small a slice of adulthood to draw firm conclusions. As discussed elsewhere (Faraone and Biederman 2016), the claims for adult-onset ADHD are all based on population as opposed to clinical studies.
Population studies are plagued by the "false positive paradox", which states that, even when false positive rates are low, many or even most diagnoses in a population study can be false.  

Another problem is that the false positive rate is sensitive to the method of diagnosis. The child diagnoses in the studies claiming the existence of adult-onset ADHDused reports from parents and/or teachers but the adult diagnoses were based on self-report. Self-reports of ADHD in adults are less reliable than informant reports, which raises concerns about measurement error.   Another longitudinal study found that current symptoms of ADHD were under-reported by adults who had had ADHD in childhood and over-reported by adults who did not have ADHD in childhood(Sibley, Pelham, et al. 2012).   These issues strongly suggest that the studies claiming the existence of adult-onset ADHD underestimated the prevalence of persistent ADHD and overestimated the prevalence of adult-onset ADHD.  Thus, we cannot yet accept the conclusion that most adults referred to clinicians with ADHD symptoms will not have a history of ADHD in youth.

The new papers conclude that child and adult ADHD are "distinct syndromes", "that adult ADHD is more complex than a straightforward continuation of the childhood disorder" and that adult ADHD is "not a neurodevelopmental disorder". These conclusions are provocative, suggesting a paradigm shift in how we view adulthood and childhood ADHD.   Yet they seem premature.  In these studies, people were categorized as adult-onset ADHD if full-threshold add had not been diagnosed in childhood.  Yet, in all of these population studies, there was substantial evidence that the adult-onset cases were not neurotypical in adulthood (Faraone and Biederman 2016).  Notably, in a study of referred cases, one-third of late adolescent and adult-onset cases had childhood histories of ODD, CD, and school failure(Chandra, Biederman, et al. 2016).   Thus, many of the "adult onsets" of ADHD appear to have had neurodevelopmental roots. 

Looking through a more parsimonious lens, Faraone and Biederman(2016)proposed that the putative cases of adult-onset ADHD reflect the existence of subthreshold childhood ADHD that emerges with full threshold diagnostic criteria in adulthood.   Other work shows that subthreshold ADHD in childhood predicts onsets of full-threshold ADHD in adolescence(Lecendreux, Konofal, et al. 2015).   Why is onset delayed in subthreshold cases? One possibility is that intellectual and social supports help subthreshold ADHD youth compensate in early life, with decompensation occurring when supports are removed in adulthood or the challenges of life increase.  A related possibility is that the subthreshold cases are at the lower end of a dimensional liability spectrum that indexes risk for onset of ADHD symptoms and impairments.  This is consistent with the idea that ADHD is an extreme form of a dimensional trait, which is supported by twin and molecular genetic studies(Larsson, Anckarsater, et al. 2012, Lee, Ripke, et al. 2013).  These data suggest that disorders emerge when risk factors accumulate over time to exceed a threshold.  Those with lower levels of risk at birth will take longer to accumulate sufficient risk factors and longer to onset.

In conclusion, it is premature to accept the idea that there exists an adult-onset form of ADHD that does not have its roots in neurodevelopment and is not expressed in childhood.   It is, however, the right time to carefully study apparent cases of adult-onset ADHD to test the idea that they are late manifestations of a subthreshold childhood condition.

Agnew-Blais, J. C., G.V. Polanczyk, A. Danese, J. Wertz, T. E. Moffitt and L. Arseneault (2016)."Persistence, Remission and Emergence of ADHD in Young Adulthood:Resultsfrom a Longitudinal, Prospective Population-Based Cohort." JAMA.Caye, A., T. B.-M. Rocha, L. Luciana Anselmi, J. Murray, A. M.B. Menezes, F. C. Barros, H. Gonçalves, F. Wehrmeister, C. M. Jensen, H.-C.Steinhausen, J. M. Swanson, C. Kieling and L. A. Rohde (2016). "ADHD doesnot always begin in childhood: E 1 vidence from a large birth cohort." JAMA.
Chandra, S., J. Biederman and S. V. Faraone (2016)."Assessing the Validity of  the Ageat Onset Criterion for Diagnosing ADHD in DSM-5." J Atten Disord.
Faraone, S. V. and J. Biederman (2016). "CanAttention-Deficit/Hyperactivity Disorder Onset Occur in Adulthood?" JAMAPsychiatry.
Larsson, H., H. Anckarsater, M. Rastam, Z. Chang and P.Lichtenstein (2012). "Childhood attention-deficit hyperactivity disorderas an extreme of a continuous trait: a quantitative genetic study of 8,500 twinpairs." J Child Psychol Psychiatry53(1): 73-80.
Lecendreux, M., E. Konofal, S. Cortese and S. V. Faraone(2015). "A 4-year follow-up of attention-deficit/hyperactivity disorder ina population sample." J Clin Psychiatry76(6): 712-719.
Lee, S. H., S. Ripke, B. M. Neale, S. V. Faraone, S. M.Purcell, R. H. Perlis, B. J. Mowry, A. Thapar, M. E. Goddard, J. S. Witte, D.Absher, I. Agartz, H. Akil, F. Amin, O. A. Andreassen, A. Anjorin, R. Anney, V.Anttila, D. E. Arking, P. Asherson, M. H. Azevedo, L. Backlund, J. A. Badner,A. J. Bailey, T. Banaschewski, J. D. Barchas, M. R. Barnes, T. B. Barrett, N.Bass, A. Battaglia, M. Bauer, M. Bayes, F. Bellivier, S. E. Bergen, W.Berrettini, C. Betancur, T. Bettecken, J. Biederman, E. B. Binder, D. W. Black,D. H. Blackwood, C. S. Bloss, M. Boehnke, D. I. Boomsma, G. Breen, R. Breuer,R. Bruggeman, P. Cormican, N. G. Buccola, J. K. Buitelaar, W. E. Bunney, J. D.Buxbaum, W. F. Byerley, E. M. Byrne, S. Caesar, W. Cahn, R. M. Cantor, M.Casas, A. Chakravarti, K. Chambert, K. Choudhury, S. Cichon, C. R. Cloninger,D. A. Collier, E. H. Cook, H. Coon, B. Cormand, A. Corvin, W. H. Coryell, D. W.Craig, I. W. Craig, J. Crosbie, M. L. Cuccaro, D. Curtis, D. Czamara, S. Datta,G. Dawson, R. Day, E. J. De Geus, F. Degenhardt, S. Djurovic, G. J. Donohoe, A.E. Doyle, J. Duan, F. Dudbridge, E. Duketis, R. P. Ebstein, H. J. Edenberg, J.Elia, S. Ennis, B. Etain, A. Fanous, A. E. Farmer, I. N. Ferrier, M.Flickinger, E. Fombonne, T. Foroud, J. Frank, B. Franke, C. Fraser, R.Freedman, N. B. Freimer, C. M. Freitag, M. Friedl, L. Frisen, L. Gallagher, P.V. Gejman, L. Georgieva, E. S. Gershon, D. H. Geschwind, I. Giegling, M. Gill,S. D. Gordon, K. Gordon-Smith, E. K. Green, T. A. Greenwood, D. E. Grice, M.Gross, D. Grozeva, W. Guan, H. Gurling, L. De Haan, J. L. Haines, H. Hakonarson,J. Hallmayer, S. P. Hamilton, M. L. Hamshere, T. F. Hansen, A. M. Hartmann, M.Hautzinger, A. C. Heath, A. K. Henders, S. Herms, I. B. Hickie, M. Hipolito, S.Hoefels, P. A. Holmans, F. Holsboer, W. J. Hoogendijk, J. J. Hottenga, C. M.Hultman, V. Hus, A. Ingason, M. Ising, S. Jamain, E. G. Jones, I. Jones, L.Jones, J. Y. Tzeng, A. K. Kahler, R. S. Kahn, R. Kandaswamy, M. C. Keller, J.L. Kennedy, E. Kenny, L. Kent, Y. Kim, G. K. Kirov, S. M. Klauck, L. Klei, J.A. Knowles, M. A. Kohli, D. L. Koller, B. Konte, A. Korszun, L. Krabbendam, R.Krasucki, J. Kuntsi, P. Kwan, M. Landen, N. Langstrom, M. Lathrop, J. Lawrence,W. B. Lawson, M. Leboyer, D. H. Ledbetter, P. H. Lee, T. Lencz, K. P. Lesch, D.F. Levinson, C. M. Lewis, J. Li, P. Lichtenstein, J. A. Lieberman, D. Y. Lin,D. H. Linszen, C. Liu, F. W. Lohoff, S. K. Loo, C. Lord, J. K. Lowe, S. Lucae,D. J. MacIntyre, P. A. Madden, E. Maestrini, P. K. Magnusson, P. B. Mahon, W.Maier, A. K. Malhotra, S. M. Mane, C. L. Martin, N. G. Martin, M. Mattheisen,K. Matthews, M. Mattingsdal, S. A. McCarroll, K. A. McGhee, J. J. McGough, P.J. McGrath, P. McGuffin, M. G. McInnis, A. McIntosh, R. McKinney, A. W. McLean,F. J. McMahon, W. M. McMahon, A. McQuillin, H. Medeiros, S. E. Medland, S.Meier, I. Melle, F. Meng, J. Meyer, C. M. Middeldorp, L. Middleton, V.Milanova, A. Miranda, A. P. Monaco, G. W. Montgomery, J. L. Moran, D.Moreno-De-Luca, G. Morken, D. W. Morris, E. M. Morrow, V. Moskvina, P. Muglia,T. W. Muhleisen, W. J. Muir, B. Muller-Myhsok, M. Murtha, R. M. Myers, I.Myin-Germeys, M. C. Neale, S. F. Nelson, C. M. Nievergelt, I. Nikolov, V.Nimgaonkar, W. A. Nolen, M. M. Nothen, J. I. Nurnberger, E. A. Nwulia, D. R.Nyholt, C. O'Dushlaine, R. D. Oades, A. Olincy, G. Oliveira, L. Olsen, R. A.Ophoff, U. Osby, M. J. Owen, A. Palotie, J. R. Parr, A. D. Paterson, C. N.Pato, M. T. Pato, B. W. Penninx, M. L. Pergadia, M. A. Pericak-Vance, B. S.Pickard, J. Pimm, J. Piven, D. Posthuma, J. B. Potash, F. Poustka, P. Propping,V. Puri, D. J. Quested, E. M. Quinn, J. A. Ramos-Quiroga, H. B. Rasmussen, S.Raychaudhuri, K. Rehnstrom, A. Reif, M. Ribases, J. P. Rice, M. Rietschel, K.Roeder, H. Roeyers, L. Rossin, A. Rothenberger, G. Rouleau, D. Ruderfer, D.Rujescu, A. R. Sanders, S. J. Sanders, S. L. Santangelo, J. A. Sergeant, R.Schachar, M. Schalling, A. F. Schatzberg, W. A. Scheftner, G. D. Schellenberg,S. W. Scherer, N. J. Schork, T. G. Schulze, J. Schumacher, M. Schwarz, E.Scolnick, L. J. Scott, J. Shi, P. D. Shilling, S. I. Shyn, J. M. Silverman, S.L. Slager, S. L. Smalley, J. H. Smit, E. N. Smith, E. J. Sonuga-Barke, D. StClair, M. State, M. Steffens, H. C. Steinhausen, J. S. Strauss, J. Strohmaier,T. S. Stroup, J. S. Sutcliffe, P. Szatmari, S. Szelinger, S. Thirumalai, R. C.Thompson, A. A. Todorov, F. Tozzi, J. Treutlein, M. Uhr, E. J. van den Oord, G.Van Grootheest, J. Van Os, A. M. Vicente, V. J. Vieland, J. B. Vincent, P. M.Visscher, C. A. Walsh, T. H. Wassink, S. J. Watson, M. M. Weissman, T. Werge,T. F. Wienker, E. M. Wijsman, G. Willemsen, N. Williams, A. J. Willsey, S. H.Witt, W. Xu, A. H. Young, T. W. Yu, S. Zammit, P. P. Zandi, P. Zhang, F. G.Zitman, S. Zollner, B. Devlin, J. R. Kelsoe, P. Sklar, M. J. Daly, M. C.O'Donovan, N. Craddock, P. F. Sullivan, J. W. Smoller, K. S. Kendler and N. R.Wray (2013). "Genetic relationship between five psychiatric disordersestimated from genome-wide SNPs." Nat Genet45(9): 984-994.
Moffitt, T. E., R. Houts, P. Asherson, D. W. Belsky, D. L.Corcoran, M. Hammerle, H. Harrington, S. Hogan, M. H. Meier, G. V. Polanczyk,R. Poulton, S. Ramrakha, K. Sugden, B. Williams, L. A. Rohde and A. Caspi(2015). "Is Adult ADHD a Childhood-Onset Neurodevelopmental Disorder?Evidence From a Four-Decade Longitudinal Cohort Study." Am J Psychiatry:appiajp201514101266.
Sibley, M. H., W. E. Pelham, B.S. Molina, E. M. Gnagy, J. G. Waxmonsky, D. A. Waschbusch, K. J. Derefinko, B.T. Wymbs, A. C. Garefino, D. E. Babinski and A. B. Kuriyan (2012). "Whendiagnosing ADHD in young adults emphasize informant reports, DSM items, and impairment."J Consult Clin Psychol80(6):1052-1061.

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“Do I Have ADHD?”: Diagnosis of ADHD in Adulthood and Its Mimics in the Neurology Clinic

A recent in-depth clinical review published by the American Academy of Neurology examines how ADHD manifests in adulthood and how neurologists can differentiate it from other causes of attention problems. 

Recognition of ADHD in adults by clinicians is often delayed or misdiagnosed due to overlapping symptoms with anxiety, depression, sleep disorders, and life stressors. Conversely, as ADHD in adults becomes more widely acknowledged, largely due to increased public awareness and social media trends, clinicians need to take extra care not to incorrectly diagnose patients with ADHD. This publication aims to shine a light on both sides of this issue and highlight the importance of clinicians being trained in proper ADHD screening. 

ADHD Symptom Overlaps and Differential Diagnosis 

The article highlights how many adults come to neurology clinics convinced they have ADHD after online quizzes or watching others get diagnosed. True ADHD must be differentiated from issues with shared signs and symptoms such as poor sleep, anxiety, depression, or even OCD or Bipolar Disorder. This is a high-level clinical skill called differential diagnosis.

  • Sleep Issues- This is one of the most common causes of attention and focus problems that resemble ADHD in adults. Chronic sleep deprivation can lead to issues like distractibility, forgetfulness, and emotional instability, which may be mistaken for ADHD symptoms, especially if people don’t realize how long-term sleep loss has affected them. Clinicians are encouraged to ask about sleep habits and use tools like the Epworth Sleepiness Scale.

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  • Anxiety Disorders- Anxiety is common in adults with ADHD, but a patient with anxiety who does not have ADHD may present with signs and symptoms that overlap with ADHD. A key difference between anxiety and ADHD is that people with ADHD often get distracted even when relaxed or doing something enjoyable without realizing it. Those with anxiety usually feel tense, guilty, and very aware of their distraction.

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  • Depression- Depression can cause trouble with focus, energy, and motivation, again, often overlapping with or mimicking symptoms of ADHD. Since both conditions are common, they can also occur together, making it important to look at when symptoms started. If attention problems were present before any depressive episodes, it may point to ADHD, but in unclear cases, treating depression first and then reassessing can help clarify the diagnosis.

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  • OCD- Some people with ADHD experience distressing, repetitive thoughts that feel like OCD, even if they haven’t been diagnosed with it. These thoughts can cause anxiety or sadness, even when the person knows they’re unlikely or irrational, but unlike OCD, there are no compulsive behaviors. In some cases, ADHD medication helps reduce these thoughts by improving focus and emotional regulation.

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  • Autism- Adults with ASD are more likely to also have ADHD, and in some cases, ADHD symptoms, such as missing social cues or acting impulsively, can be mistaken for autism. This overlap can sometimes make diagnosis more complicated.

The author of the article, Dr. Mierau, provides detailed clinical strategies such as asking open-ended questions, exploring how symptoms show up at home and at work, and watching for patterns like chronic lateness or emotional overeating. (This paper points out that, while not included in the DSM-VI, food cravings and binge behaviors are commonly found in patients with ADHD.)

This review correctly emphasizes that neuropsychological testing is not necessary for diagnosis. Instead, a thorough clinical interview, including a detailed family history and behavioral observation, can be more telling. 

Conclusion: Real Barriers to Proper ADHD Diagnosis

The review article closes with a call to action: the biggest obstacle isn’t diagnosing or treating ADHD, it’s access. Adults struggle with pharmacy shortages, no-refill laws, and insurance hurdles, despite research showing treatment reduces mortality and improves life quality. Dr. Mierau argues for more trained providers, better public education, and policy changes to reduce stigma and expand access.

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July 31, 2025

Updates on ADHD and Vitamin D

The Background on ADHD and Vitamin D: 

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In a blog published in the early days of The ADHD Evidence Project, we discussed an Iranian study examining the association between Vitamin D levels and ADHD in children. The meta-analysis combined 13 studies for a total of 10,344 participants. The researchers found that youth with ADHD had "modest but significant" lower serum concentrations of 25-hydroxyvitamin D compared to those without ADHD.

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They also identified four prospective studies that compared maternal vitamin D levels with the subsequent development of ADHD symptoms in their children. Two of these used maternal serum levels, and two used umbilical cord serum levels. Together, these studies found that low maternal vitamin D levels were associated with a 40% higher risk of ADHD in their children. 

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Ultimately, the researchers noted that this result "should be considered with caution" because it was heavily dependent on one of the prospective studies included in the analysis. We concluded our blog by pointing out that further research, including more longitudinal studies, is needed before clinicians should start recommending vitamin D supplementation to ADHD patients. 

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Further Research: 

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Since publishing that initial blog, several more studies have been published about this association. 

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The World Federation of Societies of Biological Psychiatry (WFSBP) and the Canadian Network for Mood and Anxiety Disorders (CANMAT) convened an international task force involving 31 leading academics and clinicians from 15 countries between 2019 and 2021. Their goal was to provide a definitive, evidence-based report to assist clinicians in making decisions around the recommendation of nutraceuticals and phytoceuticals for major psychiatric disorders.

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For ADHD, the guidelines found only weak support for micronutrients and vitamin D in treatment. Overall, the task force concluded that nutraceuticals and phytoceuticals currently offer very limited evidence‑based benefit for ADHD management.

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Another study published in 2023 systematically assessed the results of previously published studies to examine the associations between maternal vitamin D levels, measured as circulating 25(OH)D levels in pregnancy or at birth, and later offspring psychiatric outcomes. This study found a clear association between maternal vitamin D deficiency and subsequent offspring ADHD. They concluded, “Future studies with larger sample sizes, longer follow-up periods, and prenatal vitamin D assessed at multiple time points are needed.”  To that, I will add that studies of this issue should use genetically informed designs to avoid confounding.

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Conclusion:

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Taking into account the updated research on the topic, there does seem to be an association between low prenatal vitamin D levels and the risk of subsequent offspring ADHD, but it is too soon to say it is a causal relationship due to the possibility of confounding. There is no high-quality evidence, however, that supplementing with vitamin D will significantly reduce symptoms in current ADHD patients. 

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July 28, 2025

What Metabolites Tell Us About ADHD — And What This Means for Diet and Treatment

New research has uncovered important links between certain blood metabolites and ADHD by using a genetic method called Mendelian randomization. This approach leverages natural genetic differences to help identify which metabolites might actually cause changes in ADHD risk, offering stronger clues than traditional observational studies.

Key Metabolic Pathways Involved:

The study found 42 plasma metabolites with a causal relationship to ADHD. Most fall into two major groups:

  • Amino acid metabolites from protein metabolism, including those related to tyrosine, methionine, cysteine, and taurine.

  • Fatty acids, especially long-chain polyunsaturated fatty acids (PUFAs) like DHA and EPA, important for brain function.

What Does This Mean for Diet and ADHD?

Since many metabolites come from dietary sources like proteins and fats this supports the idea that diet could influence metabolic pathways involved in ADHD. However, because the study focused on genetic influences on metabolite levels, it doesn’t directly prove that dietary changes will have the same effects.

Notable Metabolites:

  • 3-Methoxytyramine sulfate (MTS): linked to dopamine metabolism, higher genetic levels of MTS were associated with a lower risk of ADHD. Dopamine plays a crucial role in attention and behavior.

  • DHA and EPA: Omega-3 fatty acids abundant in the brain; higher levels were linked to reduced ADHD risk, supporting existing research on omega-3 supplements.

  • N-acetylneuraminate: Involved in brain development and immune function, with higher levels linked to increased ADHD risk, though more research is needed to understand this.

Five metabolites showed bidirectional links with ADHD, meaning genetic risk for ADHD also affects their levels which suggests a complex interaction between brain function and metabolism.

Twelve ADHD-related metabolites are targets of existing drugs or supplements, including:

  • Acetylcysteine: an antioxidant used in various treatments.

  • DHA supplements: widely used to support brain and heart health.

What This Study Doesn’t Show

While these findings highlight biological pathways, they don’t prove that changing diet will directly alter ADHD symptoms. Metabolite levels are shaped by genetics plus environment, lifestyle, and health factors, which require further study.

Conclusion: 

This research provides stronger evidence of metabolic pathways involved in ADHD and points to new possibilities for diagnosis and treatment. Future work could explore how diet or drugs might safely adjust these metabolites to help manage ADHD.

While this study strengthens the link between amino acid and fatty acid metabolism and ADHD risk, suggesting that diet could play a role, ultimately more research is still needed before experts could use this research to give specific nutritional advice.

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July 21, 2025

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