Synesthesia Disorder: Causes, Impacts, and Management Strategies

Synesthesia is a fascinating neurological condition or trait that can cause a person to experience unique sensory crossover phenomena.  A person with synesthesia may perceive certain visuals and sensations with a particular sensory input, resulting in a mixed sensory experience. These synesthetic experiences, which connect two senses, can be positive, negative, or neutral. Thus, synesthesia is considered a sensory difference or neurodivergent trait rather than a disorder.

For non-synesthetes, it may be helpful to explore how a synesthete’s brain differs from a neurotypical brain, and how living with the involuntary experiences of a sensory condition can offer creative and cognitive benefits, challenges, and obstacles. Having synesthesia means looking at the world in a different way, which can cause feelings of anxiety or sensory overload. With a firm understanding of synesthesia as a neurodivergent trait, it may be possible to leverage synesthesia’s advantages and cope with any unpleasant effects. 

Synesthesia: When your brain routes sensory information through multiple unrelated senses, causing you to experience more than one sense simultaneously 

Types of synesthesia

There are many types of synesthesia, and experiences of synesthesia can vary widely. Synesthetic experiences can involve any of the five senses, emotions, characterizations, and written or spoken language. Some common forms of synesthesia include the following. 

Grapheme-color synesthesia

Grapheme-color synesthesia involves associating specific colors with letters, numbers, or symbols. For example, someone with grapheme-color synesthesia may perceive the letter "A" as always being red or the number "five" as green.

Chromesthesia (sound-to-color synesthesia)

This type of synesthesia is characterized by perceiving sounds as vivid colors. When a synesthete hears music or other sounds, they may experience a simultaneous mental or visual display of colors and shapes associated with each sound.

Number-form synesthesia

Number-form synesthesia involves perceiving numbers as having specific spatial arrangements or forms. These individuals may visualize numbers organized in particular patterns, such as a mental number line, spiral, or other spatial configuration.

Taste-color synesthesia

Taste-color synesthesia is characterized by assigning particular colors to specific tastes or flavors. For example, a synesthete may see a yellow or golden hue when eating peanut butter or a bright orange metallic figure when drinking soda.

Spatial sequence synesthesia

Individuals with spatial sequence synesthesia perceive sequences of numbers, months, or days of the week as having specific spatial locations. They may see these sequences with lattice spacing (conceptual synesthesia) or a mental map, with the sequences appearing to the individual as a physical shape or presence.

Lexical-gustatory synesthesia

Lexical-gustatory synesthesia involves “tasting” words or sounds. For example, a synesthete may sense that the word “door” tastes like chocolate.

Ordinal linguistic personification

Individuals with ordinal linguistic synesthesia associate personalities or traits with ordered sequences, such as:

• Numbers
• Letters
• Days of the week
• Months
• Years

Associative synesthesia vs projective synesthesia

Individuals living with synesthesia may experience the phenomenon in different ways. Some may experience associative synesthesia, where the association occurs in the mind, without seeing visual forms. For example, a person may feel like a sound is the color green, even if they continue seeing everything in the same color. 

Unlike individuals experiencing associative synesthesia, people living with projective synesthesia may actually experience changes in their reality. For a person with projective synesthesia, sounds or experiences may change their sensory reality; instead of feeling an association with a color, they may actually see that color.  

Mirror touch synesthesia

People living with mirror touch synesthesia may experience tactile sensations when another person experiences a physical touch. For example, when mirror touch synesthetes watch a person get hurt or injured, they may feel pain or tingling in corresponding areas of the body. 

Auditory-tactile and movement-based forms

Some individuals may experience different forms of synesthesia, including auditory tactile synesthesia. This form of synesthesia may be experienced when a person feels sounds as they occur. For example, a bouncing ball may be associated with a particular feeling in the body, which can take multiple forms, including: 

• Tingling
• Pressure
• Tapping on the shoulder
• Buzzing sensations
• Vibrations

Swimming style synesthesia 

Individuals with swimming style synesthesia may see different colors depending on which swim stroke is occurring while swimming or watching swimming. 

How common is synesthesia?

Research suggests that 2% to 4% of the population may have some form of synesthesia, though its prevalence may vary depending on the specific type of synesthesia being considered. Different types of synesthesia have been studied to varying degrees, and their prevalence rates can differ. For example, grapheme-color synesthesia, where letters or numbers are associated with specific colors, is one of the most widely researched and reported types. It is estimated to occur in around 1% to 2% of the population.

Synesthesia appears to have a genetic component, with around 40% of people with synesthesia found to have a first-degree relative who also experiences synesthesia. Scientists are still uncovering whether there is a selective advantage for synesthesia or if it is linked to another trait. Many synesthetes may view this type of neurodivergence as an asset or a trait that makes them unique.

Is synesthesia a mental disorder or mental illness?

While synesthesia is often referred to as a "disorder," or mental illness, it may be more accurately described as a neurological condition or form of neurodivergence. Synesthetes are not necessarily impaired or dysfunctional in any way. People with these traits may embrace their unique perceptual experiences and often report them as enriching and enjoyable. Rather than a disorder, synesthesia is commonly regarded as a neurological trait—a variation in how the brain processes and perceives information. 

While synesthesia disorder is not classified as a disorder may not officially be recognized, there may be situations or rare cases in which it impacts an individual's daily life or causes distress. These impacts may occur when the synesthetic associations are overwhelming, distracting, or interfere with specific tasks or activities. Researchers with the American Psychiatric Association note that individuals experiencing certain types of synesthesia may also experience anxiety disorders more frequently. In such cases, individuals may seek support to manage their experiences.

Synesthesia and neurodiversity

Like other types of neurodivergence, synesthesia challenges the notion of a "typical" or "normal" sensory experience. It may expand one’s understanding of how individuals perceive and process sensory information, and some synesthetes may report their condition as a source of creativity or inspiration. 

Synesthesia commonly co-occurs with other forms of neurodivergence, including autism and attention-deficit hyperactivity disorder (ADHD). Advanced imaging technologies and neural mapping have shown similar mechanisms in autism and synesthesia, as both conditions involve patterns of neural connectivity between the brain’s sensory and cognition centers.

Neural mechanisms of synesthesia

The neural mechanisms underlying synesthesia are still an active area of research. When comparing the brain scans of synesthetes with those of neurotypical individuals, researchers have found notable neurological differences and identified areas of increased activation or connectivity that may be responsible for synesthetic associations. Several theories exist regarding the neurological origins and neural basis of synesthesia, including:

Cross-activation theory

This theory suggests synesthesia results from more connections between the brain’s sensory regions responsible for processing different sensory modalities. In most synesthetes, the activation of one sensory or cognitive pathway incites leads to the activation of another.

Hyperconnectivity theory

According to this theory, synesthesia arises from excess neural connections or hyperconnectivity between brain areas. These additional connections may facilitate the cross-activation and integration of sensory information across modalities, resulting in synesthetic perceptions and impacting cognitive and perceptual processes.

Disinhibited feedback theory

This theory proposes that synesthesia occurs because there is less control or suppression of signals between parts of the brain that process senses and those that handle higher-level thinking. In typical perception, feedback signals are suppressed, allowing for focused and distinct sensory experiences. In synesthesia, this inhibition is weakened, allowing for the blending of sensations.

Conceptual-mediation model

This model considers how, for synesthetes, brain regions involved in conceptual knowledge are often activated in addition to those involved in sensory perception. It suggests that how the brain mentally represents and categorizes different objects or concepts may play a role in synesthetic experiences.

Acquired synesthesia and rare cases

While the majority of synesthesia cases may be congenital, there are acquired forms that may occur later in life. When compared with synesthesia from birth, acquired synesthesia may be inconsistent and can fade over time. Some causes of acquired synesthesia may include: 

• Traumatic brain injuries
• Brain tumors
• Sensory deprivation
• Migraine headaches

Some people with congenital synesthesia may experience a phase change or shift in how they experience synesthesia over time. Changes may be prevalent as the brain matures, with sensations changing in intensity or type.  

Testing, diagnosis, and treatment

People who believe they are experiencing synesthesia or are having synesthesia-like experiences can take a type of synesthesia test called a synesthesia battery to determine if they are experiencing this type of neurodivergence. The key to identifying synesthesia may be consistency and stability. This means that a person with synesthesia will experience the same enhanced communication or visuals when tested during different time intervals.   

Synesthesia may not be considered a disease or disorder, and there is currently no method for treating or reducing synesthesia. In rare cases, synesthesia can cause distress and anxiety. It may be possible to have these secondary symptoms of synesthesia treated by a mental health professional through therapy and mindfulness techniques.    

Benefits of synesthesia

Synesthesia may enrich the lives of those who experience it. Some artists, musicians, and other creatives report that their synesthesia informs and inspires their work. Synesthesia may also be helpful in everyday functioning for jobs that require the use of the five senses; for example, sommeliers, perfumers, and chefs may find that their condition helps them access more profound, more complex layers of sensory information. 

In addition to creative expression, some synesthetes use their synesthetic experiences to enhance memory recall. The vivid nature of synesthetic associations may be beneficial for encoding and retrieving memories. Synesthetes may also have improved attention to detail, greater cognitive flexibility, and an increased ability to recognize patterns.   

Synesthesia can offer a unique lens through which to experience the world. It challenges the notion of a single "normal" sensory experience, highlighting the diversity of human perception or the human experience. Some synesthetes consider their condition a valuable aspect of their identity and use their unique sensory experiences to interact meaningfully with the world.

Challenges of synesthesia

While some synesthetes celebrate their sensory condition, synesthesia can also present challenges. These challenges may or may not be present and often vary depending on the specific type and intensity of the synesthetic perceptions. Below are a few to keep in mind. 

Sensory overload

Synesthetic experiences can be intense and overwhelming, especially in environments with high sensory stimulation. This overwhelming sensation can make it challenging for synesthetes to filter and focus on specific sensory inputs. In addition, if an individual has another form of neurodivergence, such as the case with autistic people, they may be hypersensitive to sensory experiences, which could lead to more frequent sensory overload. 

Cognitive load

Synesthesia can require additional cognitive resources to process and manage simultaneous sensory information, which may affect attention, concentration, and memory.

Distraction

Synesthetic perceptions' involuntary and automatic nature can be distracting, particularly when engaging in tasks that require focused attention. Synesthetes may find ignoring or separating the synesthetic sensations from a task challenging.

Social impact

Synesthetes may believe they are different or isolated due to their unique experiences. It may be challenging to communicate or explain these experiences to others, and synesthesia may be met with skepticism or misunderstanding by those unfamiliar with the condition. 

Interference with perception

In some cases, synesthetic perceptions can interfere with accurately understanding the physical world. For example, certain types of synesthesia, such as grapheme-color synesthesia, can lead to confusion or misinterpretation of visual stimuli if the synesthetic colors are perceived alongside the actual colors.

Heightened emotional response

Synesthetic experiences can sometimes evoke strong emotional responses, whether positive or negative, depending on the individual and the specific synesthetic perceptions. For example, a person with synesthesia may associate a particular food with a disgusting smell, which can lead to aversion. 

Anxiety

Some evidence suggests children with synesthesia have higher rates of anxiety disorders. More research in this area may be beneficial for adolescents and adults with this trait. 

Support options for synesthesia

Those with sensory differences may benefit from seeking mental health support from others who understand what they’re experiencing. Online forums and communities can provide valuable sources of information and resources about synesthesia and neurodivergence. Additionally, mental health support from a licensed therapist may be helpful for learning to cope with the challenges of sensory conditions. 

Online therapy platforms like BetterHelp offer individuals support from their own homes. With the ability to connect with a therapist through video chats, phone calls, or in-app messaging, those living with sensory conditions may find that online therapy allows them to be more comfortable with and in control of their therapeutic journey.

Online therapy has been found to be as effective as traditional face-to-face therapy. In one study, researchers set out to assess the effectiveness of web-based interventions delivered to children and young people with neurodevelopmental disorders like ASD and ADHD. Results showed that these online interventions were efficacious in reducing challenging symptoms associated with each of these conditions and could be helpful in assisting neurodivergent individuals.