Copper is important for the breakdown of serotonin.
Lack of copper may limit MAO activity, causing serotonin levels to climb. Ideally, your level of zinc should be higher than copper to support attention and focus, as well as for melatonin production, but it is important for copper to be available to work with MAO, especially if serotonin levels are high. Chapter 16 – Feel Good Biochemistry
This means that a high serotonin level can lead to copper deficiency?!The enzymatic degradation of serotonin (5-hydroxytryptamine, 5-HT) is mainly served by monoamine oxidase (MAO), a mitochondrial-bound enzyme requiring flavin adenine dinucleotide as a cofactor. MAO catalyzes the oxidative deamination of 5-HT by converting it into 5-hydroxy-3-indolacetaldehyde (5-HIAL), which is further processed into 5-hydroxy-3-indolacetic acid (5-HIAA) by aldehyde dehydrogenase. The Degradation of Serotonin: Role of MAO - ScienceDirect