diff --git a/epdb/models.py b/epdb/models.py
index 52930ad3..9b8bd633 100644
--- a/epdb/models.py
+++ b/epdb/models.py
@@ -2179,18 +2179,20 @@ class Pathway(EnviPathModel, AliasMixin, ScenarioMixin, AdditionalInformationMix
         return Edge.create(self, start_nodes, end_nodes, rule, name=name, description=description)
 
     def update_depths(self):
+        # Collect number of in and out links per node
         in_count = defaultdict(lambda: 0)
         out_count = defaultdict(lambda: 0)
 
         for e in self.edges:
-            # TODO check if this will remain
             for react in e.start_nodes.all():
                 out_count[str(react.uuid)] += 1
 
             for prod in e.end_nodes.all():
                 in_count[str(prod.uuid)] += 1
 
-        root_nodes = []
+        depth_map = {}
+        depth_map[0] = list()
+
         for n in self.nodes:
             num_parents = in_count[str(n.uuid)]
             if num_parents == 0:
@@ -2201,28 +2203,30 @@ class Pathway(EnviPathModel, AliasMixin, ScenarioMixin, AdditionalInformationMix
 
                 # Only root node may have children
                 if out_count[str(n.uuid)] > 0:
-                    root_nodes.append(n)
+                    depth_map[0].append(n)
 
-        levels = [root_nodes]
-        seen = set()
-        # Do a bfs to determine depths starting with level 0 a.k.a. root nodes
-        for i, level_nodes in enumerate(levels):
-            new_level = []
+        # At most depth len(nodes) is possible
+        for i in range(self.nodes.count()):
+            level_nodes = depth_map.get(i, [])
+
+            if len(level_nodes) == 0:
+                break
+
+            unique_next_level = set()
             for n in level_nodes:
-                for e in n.out_edges.all():
-                    for prod in e.end_nodes.all():
-                        if str(prod.uuid) not in seen:
-                            old_depth = prod.depth
-                            if old_depth != i + 1:
-                                prod.depth = i + 1
-                                prod.save()
+                for e in self.edges:
+                    if n in e.start_nodes.all():
+                        for p in e.end_nodes.all():
+                            unique_next_level.add(p)
 
-                            new_level.append(prod)
+            if len(unique_next_level) > 0:
+                depth_map[i + 1] = list(unique_next_level)
 
-                seen.add(str(n.uuid))
-
-            if new_level:
-                levels.append(new_level)
+        for depth, nodes in depth_map.items():
+            for n in nodes:
+                if n.depth != depth:
+                    n.depth = depth
+                    n.save()
 
 
 class Node(EnviPathModel, AliasMixin, ScenarioMixin, AdditionalInformationMixin):