Anxiety has both a biological purpose and a long list of triggers, which means the answer to this question is rarely just one thing. About 4.4% of the global population meets the criteria for a diagnosable anxiety disorder, but many more people experience stretches of heightened anxiety driven by lifestyle factors, nutritional gaps, or medical conditions they haven’t connected to their symptoms. Understanding what’s actually happening in your body, and what might be fueling it, is the first step toward feeling less stuck.
What Happens in Your Body When You Feel Anxious
Your brain has a built-in alarm system designed to protect you from threats. When something triggers it, a chain reaction starts deep in your brain: a structure called the hypothalamus signals your pituitary gland, which signals your adrenal glands (small organs sitting on top of your kidneys) to flood your bloodstream with cortisol and adrenaline. This is your stress response, and it evolved to help you run from danger or fight back.
The problem is that this system can’t tell the difference between a bear and a work deadline. Adrenaline speeds up your heart rate, tightens your muscles, and sharpens your focus. Cortisol keeps your body on high alert. When these hormones fire off repeatedly or without a clear threat, you get the familiar package of anxiety symptoms: racing heart, tight chest, shallow breathing, upset stomach, muscle tension, and a mind that won’t stop spinning. These are real physical events, not something you’re imagining. Your nervous system is doing exactly what it was designed to do, just in the wrong context.
Lifestyle Factors That Raise Your Baseline
Before looking for deeper causes, it’s worth examining the basics. Several everyday habits can quietly push your anxiety levels up without you realizing the connection.
Caffeine is one of the most common and underestimated culprits. A standard cup of coffee (80 to 120 mg of caffeine) raises cortisol levels by roughly 50% above baseline. Tea produces a milder bump of about 20%, while energy drinks fall somewhere in the middle at around 30%. If you drink coffee daily, your body does build some tolerance, but if you’ve recently increased your intake or you’re more sensitive than average, caffeine alone can create a state that feels indistinguishable from anxiety.
Sleep deprivation compounds the effect. Poor sleep disrupts the hormonal feedback loop that’s supposed to bring cortisol back down after a stressful event. When you’re underslept, your brain’s alarm system becomes more reactive, and your ability to regulate emotional responses drops. Even a few nights of poor sleep can shift your emotional baseline toward anxiety.
Screen time plays a measurable role as well, especially in larger doses. CDC data on teenagers found that those spending four or more hours a day on screens were roughly twice as likely to report anxiety symptoms compared to those with less screen time (27.1% vs. 12.3%). The light from screens also disrupts your sleep cycle, creating a feedback loop: more screen time leads to worse sleep, which leads to more anxiety, which leads to more late-night scrolling.
Blood Sugar Drops Can Feel Like Panic
One of the most surprising triggers of acute anxiety is a blood sugar crash. When your blood sugar drops too low, your body responds by releasing adrenaline and noradrenaline to push it back up. The resulting symptoms (trembling, sweating, rapid heartbeat, and a sudden wave of anxiety) can closely mimic a panic attack. If your anxiety tends to spike a few hours after eating, or when you skip meals, unstable blood sugar is worth investigating. This is especially relevant if your diet is heavy on refined carbohydrates and sugar, which cause sharp spikes followed by sharp drops.
Nutritional Deficiencies That Mimic or Worsen Anxiety
Your brain requires specific nutrients to regulate mood, and running low on them can produce psychiatric symptoms before any other obvious signs appear. Vitamin B12 deficiency is a well-documented example: anxiety can be the first noticeable symptom, appearing before the fatigue and neurological problems typically associated with low B12. People who’ve had gastric bypass surgery or have gut absorption issues are at higher risk. Elevated levels of an amino acid called homocysteine, which rise when B vitamins are low, have been found at higher levels in people with anxiety, PTSD, and depression.
Magnesium deficiency is another common contributor. Magnesium helps calm nervous system activity, and many people don’t get enough of it through diet alone. If your anxiety is accompanied by muscle cramps, poor sleep, or irritability, low magnesium is a reasonable possibility to explore with a blood test.
Medical Conditions That Present as Anxiety
Sometimes anxiety isn’t primarily a mental health issue. A range of physical conditions produce symptoms that look and feel exactly like an anxiety disorder, and they’re worth ruling out if your anxiety appeared suddenly, doesn’t respond to typical stress management, or came with other unexplained symptoms.
- Thyroid problems are among the most common medical mimics. An overactive thyroid (hyperthyroidism) floods your body with hormones that speed everything up, causing restlessness, tremors, sleep problems, heat intolerance, weight loss, and persistent anxiety. An underactive thyroid can also trigger anxiety, though through different mechanisms.
- Hormonal fluctuations tied to the menstrual cycle, perimenopause, or menopause can cause anxiety that seems to come out of nowhere. Estrogen influences several brain chemicals involved in mood regulation, and when it shifts, anxiety often follows.
- Heart arrhythmias can produce palpitations, chest tightness, and a sense of dread that’s easily mistaken for panic attacks.
- Chronic infections like Lyme disease can trigger anxiety and other neurological symptoms, sometimes as the most prominent complaint.
- Medications and supplements are a frequently overlooked cause. Many over-the-counter drugs, herbal remedies, and even food additives like MSG can provoke anxiety as a side effect. Alcohol withdrawal and stimulant misuse are also common triggers.
Georgetown University psychiatrist Robert Hedeya developed the mnemonic “THINC MED” to help clinicians remember the medical causes of anxiety: tumors, hormones, infectious diseases, nutrition, central nervous system issues, miscellaneous conditions (including autoimmune disorders and chronic pain), electrolyte abnormalities, and drugs. If you’ve been anxious for weeks without an obvious psychological reason, asking your doctor to screen for these is reasonable.
How Physical Symptoms Fuel the Cycle
Anxiety has a way of reinforcing itself through the body. When you feel anxious, your muscles tense, your breathing gets shallow, and your digestion slows or speeds up. These physical sensations then register as additional threats, which makes your brain’s alarm system fire again. Your heart races, you notice it racing, and the noticing makes it race faster. This is why anxiety so often feels like it escalates on its own, even when nothing external has changed.
Common physical symptoms include a pounding or fluttering heart, tightness in the chest or throat, nausea or stomach cramps, dizziness, tingling in the hands or face, and an inability to take a satisfying deep breath. All of these are caused by the same adrenaline and cortisol surge described earlier. They’re uncomfortable but not dangerous in themselves.
When Anxiety Becomes a Clinical Condition
Everyone feels anxious sometimes. The line between normal anxiety and a disorder is drawn based on duration, control, and impact on your life. Generalized anxiety disorder, the most common clinical form, is defined as excessive worry occurring more days than not for at least six months, about multiple areas of life, that you find difficult to control. It also requires at least three of these symptoms: restlessness or feeling on edge, easy fatigue, difficulty concentrating, irritability, muscle tension, and sleep disturbance.
The key markers that suggest your anxiety has crossed into clinical territory are functional: you’re avoiding situations you used to handle, your work performance is slipping, you’ve pulled away from friends or social activities, your sleep or appetite has changed significantly, or you’re using alcohol or other substances to cope. Difficulty with thinking, concentrating, or logical reasoning that wasn’t there before is another signal. These changes tend to creep in gradually, which makes them easy to normalize until the gap between how you’re functioning now and how you were functioning six months ago becomes impossible to ignore.
Practical Steps to Identify Your Triggers
Because anxiety has so many possible drivers, narrowing down your specific triggers is more useful than applying generic advice. Start by tracking the basics for a week or two: when your anxiety spikes, what you ate and drank beforehand, how much sleep you got the night before, and how much time you spent on screens. Patterns often emerge quickly. Someone who feels most anxious mid-morning after coffee and a sugary breakfast is dealing with a different problem than someone whose anxiety peaks at night after hours on social media.
If lifestyle adjustments don’t move the needle, a basic blood panel checking thyroid function, B12, magnesium, and blood sugar can rule out or confirm several of the medical causes. This is especially important if your anxiety started abruptly, feels purely physical, or is accompanied by symptoms like unexplained weight changes, fatigue, or heart palpitations that don’t match your stress level.
Anxiety is one of the most treatable conditions in mental health, whether the root cause turns out to be biological, environmental, nutritional, or psychological. The fact that you’re asking the question means you’ve noticed something has shifted, and that awareness is the starting point for changing it.