What Causes Learning Disorders and Why the DSM-V is Outdated

The Diagnostic and Statistical Manual, currently in its fifth edition, provides a way of labeling a variety of psychological, developmental, and cognitive syndromes. The use of these labels often gives the impression that these are discrete, well-defined illnesses, like cancer, with specific causes. However, syndromes are defined by clusters of behaviors or symptoms, not by the underlying cause.

In terms of learning disorders, the DSM-V distinguishes between learning disorders with specific impairment in reading, written expression, or mathematics. This makes it seem like there is a specific, known cause to problems acquiring skills in each of these separate domains. However, there is little scientific support for these labels or the construct of a specific learning disability.

Historically, scientists and clinicians assumed that there were precise, innate, cognitive “modules” that reflected skills critical to math, reading, or writing. This led to a single-deficit model of learning disorders such that it was thought each disorder had unique, discrete deficits associated with them. This is the model that most closely resembles the current DSM categories.

However, progress in cognitive neuroscience has shown that this is an overly simplistic view of both the brain and learning. A large body of scientific research now indicates that neurodevelopmental disorders (including Learning Disorders) have far more shared causes and risk factors than unique pathways. For example, reading disorders and Attention Deficit Hyperactivity Disorder (ADHD) have a partial genetic overlap. Some of the risky genes are actually very common. For example, the DAT1 allele, which is associated with ADHD, occurs in more than 50% of the general population. Because this is so common in the general population, it is more likely to be shared across many neurodevelopmental conditions.

The current conceptualization of the cause of learning disorders, and the one with the most research support, is a multi-factorial model. It is also more accurate to think of learning challenges as on a spectrum rather than discrete problems in acquiring specific skills. Most neurodevelopmental syndromes are caused by a combination of risky genes rather than a single gene. These genes then interact with early-life environments that can be protective or risky for brain development, which can lead to certain cognitive weaknesses. These cognitive factors represent a shared set of fundamental brain functions that, when compromised, lead to a host of learning and behavioral challenges. When a child has a greater number of risky genes or does not have environmental protective factors, a greater degree of cognitive weaknesses may emerge such that this child is more likely to have difficulties across a wider range of academic and social skills.