- Scientific theory would support the value of brown noise or white noise for ADHD based on two different theoretical understandings of the brain.
- Brown noise to assist with attention is generally low-risk, provided it is not excessively loud.
- Brown noise has not been formally proven to help ADHD, and more research is needed.
In recent months the internet has been abuzz with exciting reports of benefits for ADHD from brown noise. Brown noise is full-spectrum noise (like white noise, only lower and richer) and easily obtained by an app on a mobile phone or on the computer. Claims on the internet are that it facilitates a calm and focused mental state for tasks like studying or writing.
What is the science behind brown noise?
There are two scientific theories on why brown noise could work for ADHD, one of them an ADHD-specific theory. This first theory is called the optimal arousal theory. The idea of optimal cortical arousal for attention and performance dates back to the beginning of the 20th century in seminar work summarized as the Yerkes-Dodson law. This is an intuitive finding that optimal performance depends on optimal arousal. To simplify, if you are drowsy (low arousal) or panicked (high arousal), then your attention and focus will be poor. Arousal has to be “just right” to maximize performance.
The optimal level of arousal is not a universal constant—rather, it depends both on the nature of the task and on individual variation in stimulation sensitivity. In the mid-20th century, Hans Eysenck and others worked on the idea of individual differences in arousal dependency between what they viewed as physiological extraverts (low central arousal, needing stronger stimulation for optimal performance) and physiological introverts needed for optimal performance. That work failed to gain wide acceptance but was picked up again in the 1970s by Zentall and colleagues, who applied it to ADHD. It has been more recently modified by others into a vigilance regulation theory to conform to subsequent knowledge of the neural bases of attention and alertness.
Subsequently, a large body of electrophysiological work has suggested that many children with ADHD are characterized by low cortical arousal. When this is addressed, their attention and behavior come into focus. Think of the frontal cortex as the driver of a car—when tired, the car weaves on the road. When that part of the brain is under-active, the entire brain is not well regulated (too much noise and distraction). When the frontal cortex “wakes up,” it can suppress the rest of the brain to enable maximum attention to the task. However, it also appears that a subset of children with ADHD is over-aroused. They would be expected to have their attention get worse with brown noise. A few small studies have suggested that children with ADHD may benefit from white noise (related to brown noise).
Our own work has suggested that the arousal model works for a particular subset of children with ADHD who can be phenotypically characterized. This type of clinical differentiation helps resolve discrepancies in the field as to whether or not there is optimal arousal.
The second theory is called stochastic resonance. This is a well-established psychophysical phenomenon in which additional stimulation can enable the brain to magnify a weak signal relative to distracting stimuli. The neural function behind this phenomenon remains unclear, although the phenomenon appears to obey the laws of operation of neuron assemblies in the brain. These two theories are not mutually exclusive.
Yet, actual studies of white noise or brown noise on ADHD are few and use small samples. Thus, the science doesn’t let us conclude whether brown noise is a placebo effect or whether it has a true attentional benefit. Nonetheless, as long as the volume is not too loud (chronic loud noise in the ear can hurt your hearing), then the risks are low. If it seems to help, there’s little harm in trying. It will be very interesting to see larger, more systematic studies of brown and white noise in ADHD and the individual differences studies regarding who benefits and who doesn’t.
Please note: Dr. Nigg cannot advise on individual cases for ethical, legal, and logistical reasons.
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