Stuttering

Stuttering, also known as stammering, is a speech disorder under the category of articulation disorders in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words, or phrases, and involuntary silent pauses or blocks in which the individual who stutters is unable to produce sounds. These disruptions may be accompanied by physical tension and struggle behaviours, such as rapid eye blinking or lip shaking.

The onset of stuttering typically occurs in early childhood, usually between the ages of two and six^[1]. According to the National Institute on Deafness and Other Communication Disorders (NIDCD), it affects approximately 5-10% of all children at some point^[2]. It's more common in boys than girls, with a ratio of approximately 4:1^[3]. In the majority of cases, children recover from stuttering, but about 1% of adults continue to stutter throughout their lives^[4].

The exact cause of stuttering is not fully understood, but it is likely to involve a combination of genetic, neurological, and environmental factors.

Research has indicated that stuttering tends to run in families, and genes that may contribute to stuttering have been identified^[5]. This suggests that genetics plays a role in the disorder.

Twin studies have demonstrated a clear genetic component in stuttering. Concordance rates are significantly higher in monozygotic (identical) twins compared to dizygotic (fraternal) twins^[6]. For instance, a 2010 study by the National Institute on Deafness and Other Communication Disorders (NIDCD) found a 70-80% concordance rate in monozygotic twins, compared to a 20% concordance rate in dizygotic twins^[7].

Another key discovery in understanding the genetic basis of stuttering was made again by researchers from the NIDCD, who identified mutations in a gene called GNPTAB in individuals who stutter but not in those who do not^[8]. This gene is involved in the process by which cellular enzymes are targeted to the lysosome, a cellular compartment involved in breaking down and recycling different types of molecules^[9].

Later research by the same group also identified mutations in two other genes involved in the same lysosomal pathway: GNPTG and NAGPA^[10]. Mutations in these genes were found more frequently in people who stutter than in those who do not^[11].

Australian researchers have also been influential in researching genetic links to stuttering. Notably, Professor Angela Morgan leads the Genetics of Speech organisation, which is funded by MCRI, and has made numerous contributions to our understanding of genetic links to speech disorders.

People who stutter have differences in the way their brains process speech and language^[12]. Neuroimaging studies have shown differences in the brain structure and function in individuals who stutter compared to those who do not^[13]. This contributes to the disfluencies characteristic of stuttering.

For example, some studies have indicated that there might be a lack of asymmetry in the brain's speech and language areas^[14]. In people who do not stutter, these areas are typically larger on the left side of the brain. However, this is not always the case in those who stutter^[15]. Additionally, studies using functional imaging techniques have found that people who stutter may exhibit overactivity in the right hemisphere and reduced activity in the left hemisphere during speech^[16]. This is interesting because for most right-handed people, the left hemisphere is dominant for language tasks^[17]. These findings suggest that individuals who stutter may use their brains differently for speech and language processes than those who do not stutter^[18].

Researchers have also found differences in the neural connections in the brains of people who stutter^[19]. Some studies have indicated that there might be weaker connections in the fibre tracts (see arcuate fasciculus) that connect different language processing areas in the brain^[20]. There's also evidence for overconnectivity in other areas^[21]. This altered connectivity could disrupt the timing cues needed for smooth, fluent speech.

The dopamine hypothesis suggests that an imbalance or overactivity in the brain's dopamine system may contribute to stuttering^[22]. This idea came about when researchers observed that certain drugs which decrease dopamine levels, such as some used for Parkinson's disease, seemed to improve symptoms of stuttering^[23]. Conversely, drugs known to increase dopamine activity, like certain antipsychotics, appeared to worsen stuttering symptoms^[24].

This overactivity in the dopamine system may cause disruption in the timing and activation of motor movements required for smooth, fluent speech^[25]. While it's a promising area of research, the dopamine hypothesis is just one part of a complex picture, and not all studies have found consistent results^[26]. Also, while certain medications can reduce stuttering, they also can have significant side effects and are not typically used as a first-line treatment for stuttering^[27].

Gerald Maguire is one of the more prominent researchers on the dopamine hypothesis of stuttering, along with pharmaceutical treatment of stuttering.

The basal ganglia, a group of structures in the brain, are key components in the neural circuits that control motor activity and procedural learning, including the motor movements involved in speech^[22]. They play an essential role in the initiation and timing of movements, and they regulate activity in the motor cortex via a complex system of neural pathways^[28]. In this system, dopamine acts as a key neurotransmitter^[29].

Some researchers propose that stuttering may be linked to a dysfunction in the basal ganglia circuits, leading to timing disruptions in speech motor control^[13]. This dysfunction is related to dopamine imbalances^[26]. As mentioned earlier, the basal ganglia rely heavily on dopamine to function properly, and an overactive dopamine system could lead to disruptions in the way the basal ganglia work.

Moreover, neuroimaging studies have revealed differences in the basal ganglia between people who stutter and those who don't, providing further support for the role of these structures in stuttering^[30].

The substantia nigra pars compacta (SNc) is a critical part of the basal ganglia circuitry and plays a crucial role in the modulation of dopamine in the striatum^[31]. The SNc is a region in the brain where a large number of dopamine-producing neurons are located. These neurons project to the striatum (a component of the basal ganglia), providing the primary source of dopamine for that region^[32].

Dopamine released from the SNc plays a vital role in motor control and motor learning, modulating the excitability of striatal neurons and influencing the output of the basal ganglia circuitry^[33]. This neurotransmitter helps balance the direct and indirect pathways of the basal ganglia, both of which are critical for smooth, coordinated movement^[34]. The direct pathway facilitates desired motor patterns, while the indirect pathway inhibits undesired ones^[35].

The hypothesised overactivity of dopamine in the striatum in people who stutter might lead to a disruption of this balance, causing motor disturbances that manifest as disruptions in the flow and timing of speech^[33]. However, this is a simplified description, and the actual neural processes involved in stuttering are likely to be more complex, involving multiple brain areas and neural circuits^[22].

Environmental factors don't cause stuttering per se, but they can influence its onset, progression, and the degree of severity. Some of these factors include:

1. Family dynamics and communication styles: High expectations for a child's speech or language skills, a fast-paced home environment, or the presence of other speech and language problems in the family can exacerbate stuttering. Additionally, if family members often interrupt or do not listen to the child, it can contribute to the child's anxiety around speaking, potentially worsening their stutter^[36].

2. Stress: Situational stress, such as moving, starting a new school, or the birth of a sibling, can exacerbate stuttering in children who are already predisposed. In adults who stutter, high-stress situations or a stressful lifestyle can also make stuttering more severe^[28].

3. Other Speech and Language Problems: Children with other speech and language problems are more likely to stutter than children without these issues. This may be due to the additional cognitive and communicative load these problems place on the child^[38].

4. Bilingualism: Some research has suggested that children who are learning two languages simultaneously might be more likely to stutter. However, this doesn't mean bilingualism causes stuttering. It might be that managing two languages places additional demands on the child's developing speech and language system^[39].

5. Age of onset and gender: The time at which stuttering first starts can influence its duration and severity. Stuttering typically starts between the ages of 2 and 6 years, when speech and language skills are rapidly developing. Boys are also more likely to stutter than girls and are less likely to outgrow it without treatment^[1].

6. Reactions of others: How others react to a person's stuttering can impact its severity. Negative reactions can increase a person's anxiety around speaking, making the stutter worse^[40].
   

Stuttering often begins during early childhood when children are developing their speech and language abilities. This period, called the "preschool years," is between ages 2 and 6, and it's during this time that many children go through a phase of normal disfluency as they learn to speak^[1].

This phase is characterised by repeating words or sounds, hesitating, or using filler words like "um" and "uh." While this is typically a normal part of language development, some children don't outgrow this phase and continue to stutter. Factors that can influence the onset and progression of stuttering during these developmental years include:

1. Language Skills: Children who are developing language skills at a rapid pace may be more likely to stutter. It's possible that their speech abilities are struggling to keep up with their language development, leading to disfluencies^[41].

2. Motor Skills: Speech is a complex motor task that requires precise coordination of many different muscles and brain processes. Children who have difficulties with motor tasks or coordination might be more likely to stutter^[42].

3. Cognitive Development: Children who have cognitive impairments or developmental delays may be more likely to stutter, possibly because of difficulties with the complex cognitive processes involved in speech^[43].

4. Gender: Stuttering is more common in boys than in girls. While the reason for this isn't clear, it could be related to differences in development or brain structure between boys and girls^[44].

5. Emotional and Social Development: While emotional factors don't cause stuttering, children who are emotionally sensitive or have high levels of anxiety might be more likely to stutter, possibly because of the added stress and tension^[45].

While stuttering is primarily a neurological and speech disorder, psychological factors can certainly contribute to how the person experiences and manages their stuttering. However, it's crucial to dispel a common myth: psychological problems do not cause stuttering. Stuttering is not a result of emotional trauma or psychological issues^[1].

That said, here are ways in which psychological factors intersect with stuttering:

1. Reactions to Stuttering: Fear, anxiety, and embarrassment about stuttering can exacerbate the severity of the stutter. A person might avoid certain words or social situations to try to hide their stutter, which can make it more difficult to manage over time^[45].

2. Stress and Anxiety: High stress levels can exacerbate stuttering. Furthermore, having to manage stuttering can, in turn, lead to increased stress and anxiety, creating a kind of feedback loop^[4].

3. Self-esteem and Self-Perception: Stuttering can impact a person's self-esteem and how they perceive themselves. This might be particularly significant for children and teenagers, who are still developing their sense of self^[46].

4. Social and Emotional Well-being: Stuttering can influence social interactions and emotional well-being. It might lead to difficulties with making friends, engaging in social activities, or expressing oneself. These experiences can contribute to feelings of isolation or frustration^[47].

5. Coping Mechanisms: The way a person copes with their stuttering can also influence its progression. Some coping mechanisms, such as avoidance or denial, can actually make the stuttering worse. On the other hand, accepting the stutter and seeking appropriate treatment can lead to improved speech fluency and a better quality of life^[48].

Treatments for stuttering often depend on the age of the person affected. In young children, a common approach is indirect treatment, which involves training parents to support their child's fluency. This might include speaking slowly, providing positive feedback for fluent speech, and not interrupting or correcting their stutter.

For older children and adults, direct treatments often involve speech therapy, including fluency shaping and stuttering modification techniques. Fluency shaping techniques aim to reduce stuttering by teaching individuals to speak more slowly, regulate their breathing, and gradually increase the length of their utterances. Stuttering modification techniques, on the other hand, don't necessarily aim to eliminate stuttering, but rather to stutter more easily and with less struggle and avoidance.

1. Camperdown Program: The Camperdown Program is an evidence-based treatment for adults who stutter. The program is named after the Camperdown Clinic at the Australian Stuttering Research Centre where it was developed. The treatment involves learning a new way of speaking that reduces stuttering. The speech style is slower, and uses a continuous and smooth manner of talking, often called 'prolonged speech'. It is a self-administered treatment with minimal intervention from clinicians, often delivered via telehealth.

2. Lidcombe Program: The Lidcombe Program is a behavioural treatment for children who stutter, typically suitable for children under 6 years old. The treatment involves parents or caregivers providing feedback to the child about their speech in a supportive and positive environment. The feedback includes praising fluency and gentle correction of stuttered speech. The program was developed at the University of Sydney and is named after the suburb where the original research was conducted.

3. Westmead Program: Like the Camperdown program, the Westmead program is also for adults and adolescents who stutter. It uses a syllable-timed speech technique where each syllable is spoken with equal stress and timing. This is similar to the way in which children's stories or nursery rhymes are often spoken. It's usually administered in a one-on-one setting with a speech-language pathologist.

4. Oakville Program: The Oakville Program is a behavioural stuttering treatment targeted at young children and implemented with the supervision of a trained speech pathologist who guides parents throughout the process. The program features key elements such as Syllable-Timed Speech (STS) that encourages children to speak each syllable in time with a rhythmic beat, and contingencies which involve the parent giving speech feedback to the child after stutter-free speech or a stuttering moment. The program is structured in two stages; the first stage aims for the child to speak with minimal or no stuttering in everyday conversations, and the second stage focuses on sustaining this improvement. The Oakville Program is particularly suitable for children with severe stuttering or those who did not respond well to the Lidcombe Program, and it is commonly used for children over six years old, although those with mild stuttering might still benefit from the Lidcombe Program.

The duration of these treatments can vary considerably. In many cases, treatment may involve weekly therapy sessions over several months, followed by regular follow-up sessions to maintain the skills learned. In more intensive programs, daily therapy sessions may be provided over a period of weeks. It's worth noting that while these treatments can significantly improve speech fluency and quality of life, they do not 'cure' stuttering in the sense of completely eliminating it. Stuttering is a chronic condition, and management, rather than cure, is often the primary goal of treatment.

The best place to start with stuttering treatment is at your local speech pathology clinic. Telehealth and in-clinic appointments are usually available. Many practices have vibrant atmospheres with very bright, engaging clinicians who can give you or your child a life changing experience. Research has also shown that telehealth is an effective, and some of the brightest clinicians also choose to deliver via telehealth. Whichever method of delivery you choose, it is important to be disciplined and consistent.