In order to manage threatening situations, humans have evolved to experience a "fight or flight" response. As part of this response, when humans are confronted with a dangerous situation, their body mobilizes by sending blood away from their extremities (e.g. hands and feet) and into the major muscles, producing adrenaline, and increasing heart rate so that we are better equipped to fight off danger.
Several drugs can cause or worsen anxiety, whether in intoxication, withdrawal or from chronic use. These include alcohol, tobacco, cannabis, sedatives (including prescription benzodiazepines), opioids (including prescription pain killers and illicit drugs like heroin), stimulants (such as caffeine, cocaine and amphetamines), hallucinogens, and inhalants. While many often report self-medicating anxiety with these substances, improvements in anxiety from drugs are usually short-lived (with worsening of anxiety in the long term, sometimes with acute anxiety as soon as the drug effects wear off) and tend to be exaggerated. Acute exposure to toxic levels of benzene may cause euphoria, anxiety, and irritability lasting up to 2 weeks after the exposure.
Experiencing a chronic medical condition or severe or frequent illness can also increase risk for anxiety disorders, as well as dealing with significant illness of a family member or loved one. Given that several medical conditions have been linked to significant anxiety, in some cases a physician may perform medical tests to rule out an underlying medical condition. For instance, thyroid disease is often characterized by experiencing significant symptoms of anxiety. Menopause, heart disease, and diabetes have also been linked to anxiety symptoms. Additionally, drug abuse or withdrawal for many substances is characterized by acute anxiety, and chronic substance abuse can increase risk for developing an anxiety disorder. Anxiety can also be a side effect of certain medications. Experiencing significant sleep disturbances, such as difficulty falling asleep or staying asleep, may also be a risk factor for developing an anxiety disorder.
When we’re anxious, the body produces a stress response. The stress response is designed to give us an extra ‘boost’ of awareness and energy when we think we could be in danger. The stress response causes a number of physiological, psychological, and emotional changes in the body that enhance the body’s ability to deal with a perceived threat – to either fight or flee, which is the reason the stress response is often referred to as the ‘fight or flight response.’