Question: Hi Dr Barkley! 
  In one of your lectures, you described ADHD adolescents as being about 30% behind their age-level peers in terms of emotional maturation. As a teacher, I think this the most useful insight into working with students with ADHD. I'd like to be able to explain it well when I'm talking with colleagues and parents. Can you explain some of the specifics of the research that led to this number? 
  Thank you so much for doing this AMA!
Answer: The 30% rule about which I often speak is merely a rough clinically derived approximation for how far behind a typical child with ADHD may be from their more typical peers in their development of self-regulation (SR)(executive functioning, or EF).  I developed the concept while writing the first edition of my book for parents (Taking Charge of ADHD) but also while practicing clinically at the University of Massachusetts Medical Center from 1985-2002.  I was searching for a means by which to counsel parents and teachers on the extent to which such children were behind others of their age so as to get adults to understand the concept of a delay and the need to adjust one’s expectations down to a more appropriate level for a child so delayed.  Even back then, ADHD was considered to be developmental in nature and best considered as a delay in development, not a loss of previously normal functioning as in someone with an injury.  That idea was borrowed from two other neurodevelopmental disorders - intellectual disability and learning disorders.  For both, we often speak about the functional developmental level of the child in the domain of their delay, in those cases intelligence and learning (reading, math, spelling, language etc.) specifically.  Indeed, in the field of intelligence research, the concept of a mental age rather than an IQ was used for years in clinical work with families of such children.  
  The rule is not based on a single scientific study of that issue, which would be far too time consuming and expensive to conduct.  Instead, I was searching for a clinical rule or concept, not one of exact scientific specification as derived from a single such study.  So I went back into my own published research studies and that of many others and simply wrote down the extent to which the ADHD group's performance differed from that of typical children in the same study and looked at a wide range of children’s ages.  I did this for a wide variety of measures of EF, child social behaviors, and others.  The range of deficits was from about 25-41% or so.  The average was 32% but that is not as good for clinical use as is using a nice round number when speaking to parents.  So I rounded it down to 30%.  On average, then, a child with ADHD seems to perform about 30% behind others of their age in their EF and self-regulation.  Don't let the exact number distract you from the point of this exercise.  It is clearly a rough (imprecise) rule based on a back of the envelop type of calculation. But it worked brilliantly in advising families and others about how to understand the concept of a delay in EF, or one’s functional executive age, and start thinking about where their own child might be in that level of delay.  The point of the rule is for families to understand not just the concept of a delay but, more important to its purpose, also about the need to lower expectations to better fit with their child’s delayed level of EF/SR.    
  So there is no single scientific paper of mine to send you.  And the number itself is a crude approximation.  Instead, one views the 30% rule as an imprecise estimate so as to better convey a concept of delayed EF/SR to families and teachers and, most importantly, the need to match expectations to functional levels of EF/SR performance.  
  I am so glad to know that my work has been of value to you in understanding ADHD and its management.
content: Q: Hi Dr Barkley! 
  In one of your lectures, you described ADHD adolescents as being about 30% behind their age-level peers in terms of emotional maturation. As a teacher, I think this the most useful insight into working with students with ADHD. I'd like to be able to explain it well when I'm talking with colleagues and parents. Can you explain some of the specifics of the research that led to this number? 
  Thank you so much for doing this AMA!
   Ans: The 30% rule about which I often speak is merely a rough clinically derived approximation for how far behind a typical child with ADHD may be from their more typical peers in their development of self-regulation (SR)(executive functioning, or EF).  I developed the concept while writing the first edition of my book for parents (Taking Charge of ADHD) but also while practicing clinically at the University of Massachusetts Medical Center from 1985-2002.  I was searching for a means by which to counsel parents and teachers on the extent to which such children were behind others of their age so as to get adults to understand the concept of a delay and the need to adjust one’s expectations down to a more appropriate level for a child so delayed.  Even back then, ADHD was considered to be developmental in nature and best considered as a delay in development, not a loss of previously normal functioning as in someone with an injury.  That idea was borrowed from two other neurodevelopmental disorders - intellectual disability and learning disorders.  For both, we often speak about the functional developmental level of the child in the domain of their delay, in those cases intelligence and learning (reading, math, spelling, language etc.) specifically.  Indeed, in the field of intelligence research, the concept of a mental age rather than an IQ was used for years in clinical work with families of such children.  
  The rule is not based on a single scientific study of that issue, which would be far too time consuming and expensive to conduct.  Instead, I was searching for a clinical rule or concept, not one of exact scientific specification as derived from a single such study.  So I went back into my own published research studies and that of many others and simply wrote down the extent to which the ADHD group's performance differed from that of typical children in the same study and looked at a wide range of children’s ages.  I did this for a wide variety of measures of EF, child social behaviors, and others.  The range of deficits was from about 25-41% or so.  The average was 32% but that is not as good for clinical use as is using a nice round number when speaking to parents.  So I rounded it down to 30%.  On average, then, a child with ADHD seems to perform about 30% behind others of their age in their EF and self-regulation.  Don't let the exact number distract you from the point of this exercise.  It is clearly a rough (imprecise) rule based on a back of the envelop type of calculation. But it worked brilliantly in advising families and others about how to understand the concept of a delay in EF, or one’s functional executive age, and start thinking about where their own child might be in that level of delay.  The point of the rule is for families to understand not just the concept of a delay but, more important to its purpose, also about the need to lower expectations to better fit with their child’s delayed level of EF/SR.    
  So there is no single scientific paper of mine to send you.  And the number itself is a crude approximation.  Instead, one views the 30% rule as an imprecise estimate so as to better convey a concept of delayed EF/SR to families and teachers and, most importantly, the need to match expectations to functional levels of EF/SR performance.  
  I am so glad to know that my work has been of value to you in understanding ADHD and its management.