Brain waves & anxiety

An EEG (electroencephalogram) records electrical activity in the brain usually via electrodes placed on the surface of the head.
They are usually used to look for seizure activity or other abnormalities but can also be used to map activity related to symptoms of depression, anxiety, insomnia, attention and memory deficits.

Types of brain waves

Measured in frequency or Hz (cycles per second)
Delta 0.2-3.0 Hz - slow waves associated with very deep dreamless sleep. Predominant in newborns but should not be dominant in adults (excess delta waves can be associated with brain damage) when awake. Associated with the release of growth hormone, healing and the 'resetting' of your internal clock.
Theta 3-8 Hz - daydream like states, drowsiness, dreaming sleep (REM). Excess is associated with attention problems. Associated with the production of catecholamines. The state most receptive to hypnosis.
Alpha 8-12 Hz - (eg. lower wave pattern in image above) relaxed wakefulness, or light REM sleep. Associated with the production of serotonin (which modulates sleep, anger, aggression, mood in general). When you close your eyes, you start to produce more alpha waves.

• Associated with the ability to recall memories, reduce discomfort and pain and reduce stress and anxiety.
• Too little alpha wave activity can be associated with alcoholism, insomnia, anxiety.

Beta 12-27 Hz - (eg. higher wave pattern in image above) wide awake, mentally alert, concentration but also associated with flight or fight response, worry, anxiety.

• Too little beta wave activity can be associated with attention problems, and learning disabilities. Too much is associated with anxiety, insomnia

Gamma above 27 Hz - associated with formation of ideas, language and memory processing, and various types of learning. Absent during sleep induced by anaesthesia.

This chart is typical of a seizure (cluster of spiking in the middle). Each horizontal line represents a reading from an electrode on the scalp. Each vertical column represents one second of recording time (showing pulses per second).

You can tell a lot about a person simply by observing their brainwave patterns. For example, anxious people tend to produce an overabundance of high beta waves while people with ADD/ADHD tend to produce an overabundance of slower alpha/theta brainwaves. Likewise, there are differences in brain wave patterns in patients with schizophrenia and those without (plus also in their siblings, see Nature research):

Researchers have found that not only are brainwaves representative of of mental state, but they can be stimulated to change a person's mental state, and this in turn can help with a variety of mental issues.

A normal healthy person's day will show oscillations from delta/theta (sleep) to alpha (awake but relaxed) then back to delta/theta. However, many people instead have a predominance of delta/beta waves if sleep is not good and daily life is stressful in general. Some treatments for stress and anxiety have focused on stimulating more alpha waves...

Entrainment

Entrainment is a principle of physics. It is defined as the synchronization of two or more rhythmic cycles. The principles of entrainment appear in chemistry, neurology, biology, pharmacology, medicine, astronomy and more. Brainwave Entrainment refers to the brain's electrical response to rhythmic sensory stimulation, such as pulses of sound or light. 

When the brain is presented with a rhythmic stimulus, such as a drum beat for example, the rhythm is reproduced in the brain in the form of these electrical impulses. If the rhythm becomes fast and consistent enough, it can start to resemble the natural internal rhythms of the brain (brainwaves). When this happens, the brain responds by synchronizing its own electric cycles to the same rhythm. This is commonly called the Frequency Following Response (or FFR). FFR can be useful because brainwaves are very much related to mental state. For example, a 4 Hz brainwave is associated with sleep, so a 4 Hz sound pattern would help reproduce the sleep state in your brain. The same concept can be applied to many other mental states, including concentration, relaxation and meditation.