Although science has not come up with a single definitive explanation, there are solid theories that help to understand why this happens:
- One explanation suggests that when the body relaxes very quickly when falling asleep, the brain can “interpret” that sudden relaxation as a loss of control or body support. In response, it triggers a muscle contraction, which manifests as the sensation of falling.
- Another hypothesis takes our ancestors as a reference: when they slept in unstable or vulnerable conditions (for example in trees or rocks), a reflex to protect themselves from a real fall could have remained in our nervous system as a vestige.
- It is important to note that this phenomenon occurs mainly at the onset of sleep, not during the deepest phases. This strengthens the idea that it is linked to the transition between wakefulness and sleep.
Factors that can increase the frequency of these shocks
Although hypnagogic spasms can appear isolated and for no apparent reason, several factors can increase their appearance:
- Extreme fatigue: When the body is very tired, the process of “shutting down” the system occurs more abruptly, and the brain can react more intensely.
- Stimulants: caffeine and nicotine activate the nervous system, hindering the natural transition to sleep.
- Stress and anxiety: an agitated mind combined with a body that wants to relax creates the right scenario for these shocks.
- Stimulant medications: Some medications for conditions such as ADHD can increase the likelihood of these jerks.
- Irregular sleep rhythm: sleeping and waking up at very variable times affects sleep cycles and can promote these episodes.
