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Is There a Connection between Phentermine and Depression?

Lee Johnson
Lee Johnson

The connection between phentermine and depression is that the drug has been known to induce this mental state in patients who are taking the drug. Depression is a fairly rare side effect of the drug, but it has been documented as a possible outcome, although common side effects such as dry mouth, constipation and vomiting are more likely to occur. Stopping taking phentermine can also cause depression in some patients, and this reaction is particularly likely if the patient has been taking the drug for an extended period of time.

Phentermine is classified as an appetite suppressant, and it is often used alongside better diet and exercise by people who are hoping to lose weight. The drug is chemically similar to amphetamines, but the precise action of the drug isn’t known. Doctors believe that the drug acts on the parts of the brain that are responsible for regulating appetite. The link between phentermine and depression isn’t fully understood, but some professionals have theorized that the drug’s stimulation of the nervous system might cause an imbalance between the different mood-regulating neurotransmitters within the brain.

Common side effects of phentermine may include nausea and vomiting.
Common side effects of phentermine may include nausea and vomiting.

Many of the common side effects of the drug, although they do no not actively display the link between depression and phentermine, might be responsible for some patients suffering from depression when taking the drug. Common side effects include irritability, trouble sleeping and feelings of nervousness — the combination of which could easily lead a person to depression after some time. The drug also might cause impotence or a decrease in libido. These are among the most common side effects of phentermine, and if a patient experienced several of these simultaneously, depression is a plausible result, particularly if this went on for an extended period of time. Common side effects should be discussed with a doctor only if they are persistent or severe.

Phentermine may cause impotence.
Phentermine may cause impotence.

The link between phentermine and depression comes from the less common possible side effects of the drug. Uncommon side effects of the drug include dizziness, confusion and stomach pain, but these are experienced by far fewer patients. Feelings of depression are also listed among the more rare side effects, so there is a chance that patients will experience depression specifically when taking the drug. Most patients who are taking phentermine will not experience depression.

Common side effects of phentermine may include irritability and insomnia.
Common side effects of phentermine may include irritability and insomnia.

Withdrawal symptoms can occur when a patient stops taking phentermine after taking it for an extended period of time. If the patient is using the drug as part of a weight loss regimen, he or she could experience side effects when the drug is stopped. This is because the body becomes partially dependent on the drug’s effects, and the chemical imbalance within the brain might trigger depression. Phentermine and depression are therefore also connected through the potential withdrawal symptoms of the treatment.

Does Phentermine Cause Depression?

Some people taking phentermine have reported feelings of depression, hopelessness and sadness. Some patients even reported having suicidal thoughts. All of these effects are rare, so they’re not something most patients experience.

To date, not many clinical studies have focused on phentermine and depression. More research is needed to see how this prescription medicine may affect mood.

Depression is listed as a side effect of phentermine.
Depression is listed as a side effect of phentermine.

It’s possible that the risk of depression is dependent on the dose given or that people who have been depressed in the past are more likely to have problems. It’s also possible that phentermine doesn’t directly cause depression, and that the cases that have appeared are the result of secondary factors such as life changes.

Why Should You Follow the Doctor’s Instructions With Phentermine?

Phentermine isn’t designed to be taken on a long-term basis. It can be habit-forming if taken for too long, leading to addiction and withdrawal symptoms. Taking phentermine for more than a few weeks can increase your risk of becoming addicted to the drug.

Extended use of phentermine can make it less effective as the body develops a tolerance to it. Some people feel tempted to up the dosage, but that is a bad idea because of the risk of addiction. Instead, stick to the treatment plan provided by your doctor.

Always consult with your doctor before stopping phentermine. It’s generally better to lower the dosage gradually instead of stopping treatment immediately. Otherwise, you may experience severe withdrawal symptoms, including depression and extreme fatigue.

Can Phentermine Affect Your Mood?

Some of the common side effects of phentermine may have a link to feelings of sadness and depression. For example, phentermine can cause insomnia.

Insomnia and Depression

It’s well-known that sleep problems can trigger depressed feelings. People who have insomnia are 10 times more likely to develop depression than people who get a good night’s sleep each night.

When you can’t sleep, it makes it harder to control your emotions and mood. You may feel more irritable than normal and be more likely to get into an argument with friends and family members. In turn, these worries and upset feelings can make it harder for you to sleep. This cycle of stress and insomnia can easily lead to negative feelings and depression.

Overstimulated Neurotransmitters

The brain relies on several neurotransmitters, or chemical messengers, to balance your mood. The main neurotransmitters related to mood are serotonin, dopamine and norepinephrine.

Higher levels normally correspond to positive emotions, feelings of happiness and wellbeing, and even euphoria. Low levels can trigger sadness, lack of motivation, tiredness and depression.

As a stimulant, phentermine increases neurotransmitter levels. Why would it produce depression, then? It’s possible to overstimulate these chemical messengers, potentially leading to a sharp drop in production. This effect would be similar to the sugar “high” followed by a “crash” that happens after eating chocolate.

Stronger Emotional Responses

People who have had problems with depression in the past may be at a higher risk of feeling depressed while taking phentermine. More studies are needed to confirm this link, however.

The idea behind this theory is that phentermine is a stimulant. This means that it can lead to intensified emotions. Feelings of happiness can be magnified, and so can feelings of sadness.

In patients who are already vulnerable to extreme mood shifts, this effect may cause depression to return. Instead of reacting to minor worries normally, the body may produce intense feelings of panic, extreme sadness, strong anger or deep depression.

Possible Changes in Hormone Levels

The rare incidences of depression in people taking phentermine may be related to side effects of weight loss rather than the actions of the drug. Losing weight can affect hormone levels in the body, especially estrogen and testosterone. Men can experience severe depression if testosterone levels drop too far.

Women who have low levels of estrogen are more likely to become depressed or experience mood swings. This is because estrogen is involved in increasing levels of serotonin, the feel-good hormone that controls mood. When estrogen levels drop, so do serotonin levels, which is why many women experience depressed feelings during pregnancy, menopause and PMS.

Does Phentermine Help With Depression?

By helping you lose weight, phentermine may help you feel happier about yourself and increase feelings of self-confidence. Achieving positive health goals can improve mood and reduce sadness in many people.

As a stimulant, phentermine can increase levels of serotonin, dopamine and other neurotransmitters in the body, which is something many antidepressant medications also target. That said, phentermine should not be used as an antidepressant.

This drug isn't designed for a treatment of more than a few weeks. It can produce tolerance, addiction and severe withdrawal symptoms if misused, potentially leading to dangerous feelings of depression or suicidal thoughts.

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Discussion Comments


@bear78-- I agree with you. Anger and irritability do occur to a lot of people. They've even coined a term for it -- "phen rage." But depression is rare and occurs only in a small percentage of people.


@donasmrs-- Actually irritability is a common side effect. And I do think that what many people are experiencing is irritability and moodiness and not depression. Depression is different.

Of course, when these types of symptoms occur, one must go back to the doctor and tell him or her about it. A dose change may actually reduce the side effects. If the side effects are severe, then the doctor may recommend a different medication.

I don't recommend quitting the drug cold turkey though as that will cause more problems. It's important to withdraw slowly to avoid any withdrawal symptoms.


I became depressed after I started taking phentermine. Not just depressed though, I also became more sensitive, emotional, irritable and angry. I have asked friends who have used this medication as well as others online and quite a few people replied saying that they had the same symptoms. So I have no idea why depression is still being considered a rare side effect of phentermine.

I think the drug company needs to test its medications again and needs to label depression as a common side effect if it is so. I no longer take phentermine because of these side effects and I don't plan on using weight loss medications at all in the future. I've heard that many have side effects like these. In my opinion, it's just not worth it.

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    • Common side effects of phentermine may include nausea and vomiting.
      By: Tatty
      Common side effects of phentermine may include nausea and vomiting.
    • Phentermine may cause impotence.
      By: Tomasz Trojanowski
      Phentermine may cause impotence.
    • Common side effects of phentermine may include irritability and insomnia.
      By: detailblick
      Common side effects of phentermine may include irritability and insomnia.
    • Depression is listed as a side effect of phentermine.
      By: silent_47
      Depression is listed as a side effect of phentermine.