What Is Insomnia? Symptoms, Causes & When To Seek Help

What is insomnia?

Insomnia is the most common sleep disorder in the United States, affecting roughly 1 in 3 American adults each year and around 10% as a chronic condition. It is defined by ongoing difficulty falling asleep, staying asleep, or waking too early — despite having enough time and a suitable environment in which to sleep — combined with daytime symptoms such as fatigue, low mood, or impaired focus.

Insomnia is not just “a few bad nights.” To meet the clinical threshold used by the American Academy of Sleep Medicine, poor sleep must occur at least three nights per week and interfere with daytime functioning.

The most common insomnia symptoms

Insomnia shows up in both nighttime and daytime symptoms. Most people experience some combination of:

Nighttime symptoms

• Difficulty falling asleep (sleep latency over 20–30 minutes)
• Waking up during the night and struggling to return to sleep
• Waking too early in the morning
• Lying in bed feeling alert despite being physically tired
• Racing thoughts or a sense of dread at bedtime

Daytime symptoms

• Persistent fatigue or low energy
• Brain fog and trouble concentrating
• Irritability, low mood, or anxiety
• Reduced motivation or performance at work or school
• Increased reliance on caffeine to function

If you recognize several of these, our full insomnia symptom guide walks through each in more depth.

Acute vs chronic insomnia

Acute (short-term) insomnia lasts less than three months and is usually triggered by stress, grief, illness, jet lag, or a major life event. It often resolves once the trigger passes.

Chronic insomnia happens at least three nights per week for three months or longer. At this point, the original trigger may be gone but learned behaviors and anxiety about sleep keep the cycle going. Chronic insomnia typically requires a structured intervention — most often cognitive behavioral therapy for insomnia (CBT-I), the first-line treatment recommended by the American College of Physicians.

What causes insomnia?

Insomnia rarely has a single cause. The most common drivers we see in adults are:

• Stress and anxiety — the leading trigger. See our guide on night anxiety symptoms.
• Irregular sleep schedule — different bed and wake times disrupt your circadian rhythm.
• Caffeine after 2 p.m. and alcohol in the evening — both fragment deep sleep.
• Evening light and screen exposure — suppresses melatonin and delays sleep onset.
• Undiagnosed sleep apnea or restless legs — see sleep apnea symptoms.
• Hormonal changes, chronic pain, or certain medications — including some antidepressants, steroids, and decongestants.

When to see a doctor

Book an appointment with your primary-care physician or a board-certified sleep specialist if:

• Poor sleep persists three or more nights per week for over a month
• You snore loudly, gasp awake, or your partner notices pauses in breathing
• You feel dangerously sleepy while driving or working
• Insomnia is paired with low mood, anxiety, or any thoughts of self-harm
• Over-the-counter sleep aids are not helping after two weeks

Evidence-based steps to sleep better tonight

For most adults with mild to moderate insomnia, layered behavior changes resolve symptoms within two to four weeks. Start with these:

1. Anchor a fixed wake time — seven days a week. Read how to build a better sleep routine.
2. Get 10 minutes of outdoor light within 30 minutes of waking.
3. Cut caffeine after 2 p.m. and alcohol within three hours of bed.
4. Dim indoor lights and stop screens 60 minutes before bed.
5. Use the 4-7-8 breathing technique to calm the nervous system.
6. If you are awake longer than 20 minutes, get out of bed and do something quiet in dim light until sleepy.

For chronic insomnia, ask a clinician about CBT-I. It outperforms sleeping pills for long-term results and is now available through telehealth and validated apps.

Frequently asked questions