A gene has been identified that allows neurons that release serotonin to evenly spread their branches throughout the brain. Without this gene, these branches become entangled, leading to haphazard serotonin distribution, and signs of depression in mice. These observations shed light on how neuronal wiring is critical to overall brain health, while also revealing a promising new research focus for psychiatric disorders associated with serotonin imbalance -- such as depression, bipolar disorder, schizophrenia and autism.