forceful affirmation of individualism. Austrian existential psychiatrist Viktor Frankl connected depression to feelings of futility and meaninglessness. Frankl's logotherapy addressed the filling of an "existential vacuum" associated with such feelings, and may be particularly useful for depressed adolescents. Researchers theorized that depression was caused by a chemical imbalance in neurotransmitters in the brain, a theory based on observations made in the 1950s of the effects of reserpine and isoniazid in altering monoamine neurotransmitter levels and affecting depressive symptoms. During the 1960s and 70s, manic-depression came to refer to just one type of mood disorder (now most commonly known as bipolar disorder) which was distinguished from (unipolar) depression. The terms unipolar and bipolar had been coined by German psychiatrist Karl Kleist. In July 2022, British psychiatrist Joanna Moncrieff, also psychiatrist Mark Horowtiz and others proposed in a study on academic journal Molecular Psychiatry that depression is not caused by a serotonin imbalance in the human body, unlike what most of the psychiatry community points to, and that therefore anti-depressants don't work against the illness. However, such study was met with criticism from some psychiatrists, who argued the study's methodology used an indirect trace of serotonin, instead of taking direct measurements of the molecule. Moncrieff said that, despite her study's conclusions, no one should interrupt their treatment if they are taking any anti-depressant. See also References External links Emotions Neuropsychology Mental states