In one sentence, describe what the following article is about:

If someone tells you that they are considering killing themselves, you need to contact a professional immediately. Even if they ask you "not to tell anyone" or to keep this "between you two," you need to seek out help to prevent someone from hurting themselves.  You can reach the National Suicide Hotline at 1-800-273-TALK (8255) or 800-SUICIDE (784-2433). They can help you help your friend, and they can help talk someone down who is considering taking their own life.  If you or your friend would be more comfortable texting, send a message to the Crisis Text Line. Their number is 741741 in the US, 686868 in Canada, and 85258 in the UK. For more information, visit https://www.crisistextline.org. People considering suicide often experience rapid, intense personality changes once they've made their decision. Oftentimes this is negative, with the person acting withdrawn, depressed, or aggressive. But some people swing the opposite direction, suddenly becoming happier and calm despite months of low-energy and sadness. The important things to look out for are drastic, unexplained mood or personality shifts, not one specific "type" of behavior. People on the verge of suicide often "call out" to friends and family for help, broadcasting their intentions and sadness. Some comments to watch out for include:  "It would be better if I wasn't around," "you're better off without me." "Life is hopeless," "I feel like a waste of space and time." "I feel trapped," "I can't see any way out of this." Talking about unbearable and/or constant pain. Talking about ways a person could die or kill themselves. Calling to say "goodbye" or set affairs in order, especially "if anything happens to me." " Some people suffering from suicidal thoughts will take huge risks, believing their lives don't matter. This may include running red lights, excessive drinking or drug use, and dangerous, random new hobbies. When together, encourage safer, simpler activities and conversation Substance abuse, through either drugs or alcohol, is a major indicator of depression or suicidal thoughts. If someone suddenly wants to get drunk every single night you should keep your eye on them. Withdrawing from public life, often matched by sudden disinterest in previously loved hobbies and games, is a hallmark of suicidal behavior. Many people will retreat into their own worlds, feeling like there life is not worth other's time. If you feel like a friend has disappeared on you, make an effort to get in touch. See if there is a reason for their absence or if you should be worried about something serious. If you are unsure what to do, or if a friend is telling the truth, try and talk to them as much as possible. The more time you spend with them, the easier it will be to determine if you should get help. Changing or drafting a will, giving away prized possessions, and saying surprisingly deep or serious goodbyes are all indications that someone is ready to push forward with suicide. If an otherwise healthy person seems to be arranging their own death, setting aside provisions for family and friends, it is time to contact help. If you notice them searching online for ways to kill themselves or they suddenly buy a weapon, like a gun, you should be on high alert. Random purchases of knives or guns or research into recent deaths or suicides is a strong indicator that someone wants to hurt themselves, and you should consider calling Emergency Services. Some people are more disposed towards suicidal thoughts than others depending on their life and uprising. Knowing these risk factors can help you look out for your friend's safety and find help.  Previous suicide attempts. Family history of mental disorder, substance abuse, and/or suicide. Physical or sexual abuse, or exposure to extreme violence. Chronic physical and/or mental illness, including chronic pain. Incarceration. Exposure/closeness to other victims of suicide.

Summary:
Immediately contact emergency services if someone says that they want to kill or hurt themselves. Note any drastic shifts in behavior. Listen for any troubling language or statements. Prevent reckless, semi-suicidal "death wishes. Check in on friends who have withdrawn from friendly, normal behavior regularly. Recognize when someone is planning for their death. Know that a suicidal friend may be actively searching out ways to hurt themselves. Know the risk factors for suicidal tendencies.