How to Tell if Someone Is Mentally Ill: Signs to Watch For

It’s not always obvious when someone is struggling with their mental health. Unlike a broken arm or a fever, mental illness doesn’t show up on a scan or a thermometer. You might notice changes in behavior, but it’s easy to brush them off as stress, laziness, or just being "off." But those quiet shifts-sleeping too much or too little, withdrawing from friends, sudden anger, or losing interest in things they once loved-could be signs of something deeper.

What mental illness actually looks like in everyday life

Mental illness isn’t one thing. It’s a group of conditions-depression, anxiety, bipolar disorder, schizophrenia, PTSD, and more-that affect how a person thinks, feels, and behaves. And they don’t always look like what you see in movies. Someone with depression might still go to work, smile at coworkers, and post happy photos online. Someone with anxiety might be the most organized person in the office but can’t leave the house on weekends.

Here’s what to look for in real life:

• Changes in sleep: Sleeping 12 hours a day and still tired, or staying awake for three nights straight without feeling rested.
• Withdrawal: Stopping calls, skipping family dinners, avoiding social media, no longer showing up to events they used to love.
• Extreme mood swings: Going from laughing one minute to crying the next, or sudden outbursts of anger over small things.
• Loss of interest: No longer caring about hobbies, pets, relationships, or even personal hygiene.
• Unexplained physical symptoms: Constant headaches, stomach pain, or fatigue with no medical cause.
• Self-harm or risky behavior: Cutting, binge drinking, reckless driving, or talking about death in casual ways.

These aren’t just bad days. They’re patterns. And they last longer than a week or two.

Why you shouldn’t try to diagnose

You’re not a doctor. And you shouldn’t try to be one. Saying someone has "bipolar disorder" or "OCD" based on a few behaviors isn’t helpful-it’s harmful. Mislabeling someone can make them feel ashamed, misunderstood, or even more isolated.

What you can do is notice changes and respond with care. If your friend who used to run marathons now sits on the couch all day, don’t say, "You’re depressed." Say, "I’ve noticed you haven’t been out much lately. I’m here if you want to talk."

It’s not your job to name the illness. It’s your job to offer support.

What’s not mental illness

Not every odd behavior means something’s wrong. People have bad days. Some are introverted. Others are moody. Some cry easily. Others stay quiet under stress. These aren’t symptoms-they’re personality traits.

Here’s the difference:

• Personality: Someone is quiet because they’re thoughtful. They enjoy alone time. They don’t post on social media. That’s who they are.
• Change: Someone who used to post daily updates now hasn’t posted in three months. They used to text back within minutes. Now it takes days. They used to laugh at your jokes. Now they stare blankly.

The key is change. Mental illness often shows up as a shift from who someone was before.

When to speak up

Don’t wait for a crisis. If you’re worried, say something. But how you say it matters.

Here’s what works:

1. Choose a quiet moment, not in front of others.
2. Use "I" statements: "I’ve noticed you’ve been quiet lately, and I’m concerned."
3. Avoid judgment: Don’t say, "You need to snap out of it." Say, "I don’t know what you’re going through, but I care."
4. Offer help: "Would you be open to talking to someone? I can help you find a therapist."
5. Follow up: Check in again in a week. Don’t drop it after one conversation.

People don’t need fixing. They need to feel seen.

What to do if they say no

They might not be ready to talk. Or they might not believe they need help. That’s okay. You can’t force someone to accept support.

But you can still be there.

• Keep inviting them out-even if they say no.
• Send a text once in a while: "Saw this and thought of you."
• Don’t take silence personally.
• Know your limits. If you’re worried they might harm themselves, don’t wait. Contact a crisis line or go with them to the ER.

In the UK, you can call Samaritans at 116 123 for free, 24/7. If you’re with someone in immediate danger, call 999.

Common myths that stop people from getting help

There are so many lies people believe about mental illness:

• "They’re just being dramatic." Mental pain is real. It doesn’t need to be visible to be valid.
• "It’s all in their head." The brain is part of the body. A broken brain is just as real as a broken leg.
• "Therapy is for weak people." Asking for help takes courage. Most people who go to therapy are high-functioning, hardworking, and deeply resilient.
• "They’ll get over it." Depression doesn’t lift because someone "pulls themselves together." It takes treatment, time, and support.

These myths keep people silent. Your words can help break them.

What helps more than advice

People with mental illness don’t need advice. They need:

• Someone who listens without trying to fix it.
• Consistency-showing up even when they’re hard to be around.
• Normalcy-treating them like the same person they’ve always been, even when they’re struggling.
• Patience-recovery isn’t linear. There will be setbacks.

One woman I know stopped talking to her family for six months after a panic attack. Her sister didn’t push. She just sent a postcard every Tuesday. No message. Just "Thinking of you." On the seventh week, her sister got a reply: "Thanks for not giving up on me."

Final thought: You don’t need to be an expert

You don’t need a psychology degree to help someone. You just need to care enough to notice. To listen. To stay. Mental illness thrives in silence. Your attention-your quiet, steady presence-is one of the most powerful tools you have.

If you see someone slipping, don’t wait for them to ask. Say something. Be kind. Be patient. And keep showing up.