Is Inattentive ADHD Different from the Combined Type Of ADHD

At the heart of the debate over whether to give Primarily Inattentive ADHD it's own DSM-V category in the 2013 revised edition of the psychiatic diagnostic manual is the question of whether there is a substantial difference between this subtype and the other subtypes of ADHD.

Prominent researchers have argued that Predominantly Inattentive ADHD is just a continuum of other subtypes of ADHD.  They have proposed that the symptoms of the Primarily Inattentive subtype are nothing more than the symptoms of the ADHD Combined type missing a few hyperactive or impulsive symptoms.  They contend that Predominantly Inattentive ADHD is not substantially different from the other subtypes.  Other researchers have tried to lump Primarily Inattentive ADHD into the Sluggish Cognitive Tempo camp arguing that Primarily Inattentive ADHD is best described by the characteristic of slow cognitive processing.

A study done in Canada in September of 2009 tested 400 children with ADHD.  The researchers looked at Predominantly Inattentive children and children diagnosed as Combined type ADHD.  They documented the reported conduct disorders, treatment response to Ritalin, history of maternal smoking and alcohol consumption, history of maternal stress, genotypes, and birth weight in these children.

The study found that children with Combined type ADHD had a higher frequency of conduct disorders, a better response to Ritalin, a higher incidence of 5-HTT genotype, and more maternal stress during pregancy, when they were compared to Primarily Inattentive ADHD children.  These researchers reported that these findings pointed towards a separate biological process in children with Primarily Inattentive ADHD.

When studies are done today on ADHD, the subtypes are usually lumped together.  It is generally impossible to know how someone with Primarily Inattentive ADHD performed on the trial as compared to the rest of the ADHD group.  Studies done on primarily Inattentive ADHD children and adults are few and far between.

Providers treating individuals with Inattentive ADHD should be aware of the substantial characteristics differences of this subtype in order that appropriate treatment is provided, specific disorder related interventions are addressed, and  risk factor concerns are appropritately managed.

The question of whether Predominantly Inattentive ADHD is a separate disorder is important.  As long as Predominantly Inattentive ADHD is considered to be a ADHD Combined type with fewer hyperactive and impulsive symptoms, individuals with Primarily or Predominantly Inattentive ADHD will not be properly studied and this disorder will not be properly treated.


  1. Thank you for this article. My son is 7 years old. He had predominantly inattentive ADHD. My son has always been sluggish, unfocused, awkward at sports, processing issues at school and horrible handwriting. Though he is not hyper but will figit in his seat at school. We also did not know at 5 years old if he is left or right handed. Though now is is predominantly left handed but kicks with his right foot. At school the teacher wants me to put my son on medication for is inattention, but, he is listening to every work even though he may not be looking at her. His grades are above 90 on all his tests without help. He has a 5 to 1 aid but she only refocuses him at times. I am happy to find your website.

  2. I'm sorry for spelling error he HAS predominantly inattentive ADHD

  3. He sounds so much like my eldest. Great grades, appears to be not paying attention but hears everything. The position that on medication is that I try the least invasive interventions first. At the moment he appears to be holding steady with caffeine. This summer I will try to get him into a Cogmed or brain gym program of some kind to supplement the caffeine and prepare him for the rigors of middle school.

    My inattentive son may need to be on a stimulant at some point but I am going to try and hold off until his self esteem, social situation, or school work becomes a bigger problem than they are at the moment. Nice to hear from a comrade in arms :) Thanks for posting. Tess

  4. tesmesser, Its nice to hear from you also. I really never met anyone like my Thomas. Its nice to hear there is someone out there like him. I did get a scrip from my Dr. for Vyvanse but when I looked up the side effects there is no way. I definately want to start caffiene and Protein shakes for the morning as a start. How are you giving him the caffiene and how many mg's? I just bought ProtoWhey protein powder that has 35 mg of caffiene & 20 mg of protein to make a shake in the morning for him. I dont think this is enough caffiene since a cup of coffee is about 100 mg. As for Cogmed or brain Gym, I have never heard of them. I live in Long Island, NY. I will definately look into them. I didnt know how to put in my name and ended up Anonymous but will will be signing Kathytomsmom. Thanks for writing back.

  5. Hi, do you have a reference for this Canadian study? I'd like to read the details. Thanks!

  6. J Atten Disord. 2009 Sep 18. [Epub ahead of print]
    Is the Inattentive Subtype of ADHD Different From the Combined/Hyperactive Subtype?
    Grizenko N, Paci M, Joober R.

    McGill University.
    Objective: To compare the ADHD combined/hyperactive subtype (ADHD/CH) to the ADHD inattentive subtype (ADHD/I) on the level of comorbidity, treatment response, and possible etiological factors. Method: A total of 371 clinically referred children diagnosed with ADHD aged between 6 and 12 years are recruited for a double-blind, placebo-controlled trial of methylphenidate. Comorbidity, treatment response, and stress during pregnancy are assessed for each participant. Genotyping is done for the DAT, DRD4, and 5-HTT genes. Mothers report smoking or alcohol consumption during their pregnancy and their child's birth weight. Results: The ADHD/CH children show both a higher frequency of conduct disorder and good response to treatment, are exposed to more moderate stress during their mothers' pregnancy, and show a higher frequency of L/L genotype for the 5-HTT-linked polymorphic region. Conclusion: The significant differences found between the ADHD/CH and the ADHD/I subtypes raise the possibility that the two may be separate disorders.


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