Attention-deficit hyperactivity disorder, commonly known by the abbreviation “ADHD,” is characterized by two distinct sets of symptoms: those related to overactivity and behavioral impulsivity and those due to problems with focused and sustained attention.

We speak of “attention deficit disorder without hyperactivity” in cases where the symptoms of inattention clearly predominate over those of hyperactivity and impulsivity. In this article we will analyze the characteristics, symptoms and neuropsychological causes of ADHD .

Attention Deficit Hyperactivity Disorder

The third edition of the Diagnostic and Statistical Manual of Mental Disorders, usually known as “DSM-III”, appeared in 1980. In this version of the manual, the nomenclature “hyperkinetic reaction in childhood” was replaced by “attention deficit disorder”, leaving hyperactivity in the background at the diagnostic level.

This change of perspective was mainly due to the research of the Canadian psychologist Virginia Douglas, whose results suggested that the clinical nuclear aspects of this disorder are the difficulties in paying sustained attention to stimuli , in inhibiting impulses and in organizing cognitive processes.

Consequently, from the 1980s onwards, a distinction began to be made between two subtypes of attention deficit disorder: one in which the symptoms of hyperactivity, equivalent to the classic form of the syndrome, predominate, and another in which this type of sign does not exist or is less clinically relevant than inattention and/or behavioural impulsivity.

In the DSM-IV and in the 5, which has appeared very recently, two categories of symptoms are distinguished when describing ADHD: those of inattention, such as problems in organizing tasks and ease of distraction , and those of hyperactivity and impulsivity (excessive physical and verbal activity, interrupting others, etc.).

Main symptoms and clinical picture

Attention deficit disorder without hyperactivity or inattentive predominance is mainly characterized by the presence of symptoms derived from neurological problems that interfere with the mechanisms of brain inhibition. This makes it difficult for people with this disorder to maintain focused and sustained attention.

In this sense, the DSM-5 states that this variant of ADHD should be diagnosed when a child presents at least 6 of these symptoms in a marked and persistent way since before the age of 12 (in the case of adolescents and adults with 5 signs it is enough):

  • Neglect and lack of attention to academic, work and other tasks, especially in relation to details.
  • Difficulties in maintaining sustained attention in both recreational and other activities.
  • Often the person gives the impression that he or she is not listening or is absent when spoken to.
  • Failure to follow instructions leading to non-completion of tasks, not due to negativism or understanding problems.
  • Problems in organizing and planning activities, especially if they are sequential; includes inadequate time management.
  • Avoidance and lack of motivation and pleasure for tasks that require significant and sustained mental effort .
  • Frequent loss of objects important for the performance of certain activities.
  • Ease of distraction due to external stimuli and mental content unrelated to the task at hand
  • Frequent forgetfulness related to daily activities , such as doing homework, attending doctor’s visits or paying bills.

In contrast, in these cases the symptoms and signs of hyperactivity and/or impulsivity are significantly milder than those associated with attention deficits. There is also a mixed type in which important symptoms of these two main dimensions are combined.

For decades, attention deficit disorder without hyperactivity has been associated with slow cognitive time, characterized by hypoactivity, slowness, laziness and mental confusion . It is now known that it also appears in cases of predominantly hyperactive and impulsive behaviour and in other psychological disorders, so it is not specific to this problem.

Neuropsychological causes and characteristics

According to Adele Diamond’s (2006) review of the available scientific evidence, the main cognitive problem of people with ADD without hyperactivity is found in working or working memory. This set of processes allows us to store short-term information and perform operations on it.

Diamond states that the signs detected in those with this disorder are not so much due to their greater facility for distraction or behavioral inhibition, which has often been proposed, but rather to the fact that they are easily bored by chronic cerebral hypoactivity . This would explain their lack of motivation for many tasks.

At a biological-structural level these problems seem to be related to the connections between the frontal and parietal crust. While motor and executive functions, such as behavioral inhibition and planning, depend primarily on the frontal lobes of the brain, the parietal lobes are concerned with symbolic and arithmetic processing, among other functions.

Diamond’s meta-analysis suggests that the differences detected between inattentive and hyperactive/impulsive ADHD (in terms of neurological disorders, symptoms, psychopathological comorbidities and response to medication) may be sufficient to justify the division of this disorder into two differentiated syndromes .

Bibliographic references:

  • American Psychiatric Association (2013). Diagnostic and Statistical Manual of Mental Disorders (5th Ed.). Arlington: American Psychiatric Publishing.
  • Diamond, A. (2006). Attention-deficit disorder (attention-deficit/hyperactivity disorder without hyperactivity): A neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity). Development and Psychopathology, 17(3): 807-825.