Dyslexia and other reading and writing difficulties

What is dyslexia?

Well-developed reading and writing skills are important in order to function independently in school, working life, and modern society at large. Consequently, reading and writing difficulties often constitute a troublesome functional impairment.

Research conducted over recent decades has clearly shown that reading ability is multidimensional and can initially be divided into a word decoding function and a comprehension function. By word decoding is meant the skill of quickly and accurately recognising written words. Linguistic comprehension refers to the ability to grasp meaning in words and texts, regardless of whether they are written or spoken aloud.

Based on this model, three different types of reading and comprehension problems can be defined, with partly different backgrounds and with differing support needs for the affected individuals. One group has problems that are relatively specific to word decoding. This is what we usually mean by the term dyslexia, and spelling is also often difficult in this group. A second group has no difficulties with word decoding but does have problems with linguistic comprehension (i.e., specific comprehension problems). A third group has word decoding problems that occur together with deviations in the development of linguistic comprehension. All types of problems negatively affect reading comprehension of text, but for partly different reasons.

Prevalence

There is reason to believe that both dyslexia and comprehension difficulties constitute the lower end of the normal distribution of reading and writing skills in the population. The prevalence of dyslexia and similar difficulties therefore depends partly on where the boundary for what is considered “deviant” is drawn. However, according to definitions commonly used in research and clinical contexts, 5–15% of the population have some type of reading and writing difficulty. Possibly, (specific) reading comprehension problems are more common than dyslexia.

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Causes

Reading and writing are fundamentally cultural and social skills. For a child to acquire reading and writing abilities, patient practice over several years is usually required, along with support and encouragement from teachers and parents. At the same time, research has shown that there is a strong genetic background to variation and difficulties in reading and writing ability. Some progress has also been made in understanding the neurobiological basis of reading and writing difficulties.

Most research on the causes of dyslexia and other reading problems has been conducted at a cognitive analytical level. A large number of scientific studies have shown that a core problem in dyslexia lies in the individual’s phonology, that is, a difficulty in perceiving and manipulating speech sounds, which in turn makes the connection between letters and their sounds “unstable.” Several important studies have shown that individuals with dyslexia can improve their reading if they are given training in their phonological functions, and especially in the connection between speech sounds and letters.

Other researchers have focused on visuoperceptual difficulties as a cause of dyslexia. In such research, it has, among other things, been demonstrated that individuals with dyslexia may show a general difficulty in integrating visual and auditory information, and that measures of this ability can predict reading development in children. A strongly increased research interest can be expected in the coming years regarding the possible role of visual factors in the development of dyslexia, as well as how visual and phonological factors interact during the period of learning to read. Individual differences are also receiving increasing attention, meaning that people with the same diagnosis may have different profiles of strengths and difficulties.

Children with specific comprehension problems rarely have phonological difficulties. However, other aspects of spoken language—such as vocabulary and syntax—are often weakly developed. Additional studies have shown that children with specific comprehension problems may also have impairments in certain so-called executive functions, particularly with regard to verbal working memory and planning ability.

Commonly associated problems

There are a number of other difficulties that tend to be associated with reading and writing difficulties, including:

• Mathematics difficulties – both arithmetic and mathematical problem-solving.
• ADHD – attention difficulties in particular seem to be associated with word decoding and reading comprehension.
• Low self-esteem, stress, and other emotional problems are unfortunately not uncommon, but with support and the development of personal compensatory strategies, many people can find ways to navigate their studies and working life successfully.

Recently published articles on dyslexia

Åsberg Johnels J, Galazka MA, Sundqvist M, Hadjikhani N. Left visual field bias during face perception aligns with individual differences in reading skills and is absent in dyslexia. Br J Educ Psychol. 2025 Jun;95(2):270-279. doi: 10.1111/bjep.12559. Epub 2022 Oct 31. PMID: 36317253; PMCID: PMC12068011.